Medical Jurisprudence, called also legal or forensic medicine, the employment of the principles of medical science in the administration of law. In its relations to jurisprudence, medical learning is a branch of evidence in which the physician or surgeon is called in as an expert. There are traces both in the Jewish and Roman systems of the recognition of medical science in the application of laws; but forensic medicine cannot be said to have attained the dignity of a science until many centuries after the completion of the Justinian code, certainly not until anatomy was studied in the human subject in the 14-th century; perhaps not before the publication of the Carolinian criminal code in 1552. The Roman law had referred all medical questions which arose in legal processes to "the authority of the learned Hippocrates." The code of Charles V. enjoined the magistrate, in all cases of doubt respecting asserted pregnancy, infanticide, the means of homicide, and in other cases of death by violence, to consult the opinions of medical men. During the latter part of the 16tb century and the earlier part of the 17th, legal medicine made marked progress. Ambroise Pare published during that time a treatise upon tardy births.

Fortunatus Fidelis compiled and published at Palermo in 1602 all that was then known of medical science. At Rome, about 20 years later, Paolo Bacehia, or, as he is usually called, Paulus Bacchias, commenced the publication of his Quwstiones Medico-Legates. This work appeared in successive volumes between the years 1021 and 1050, and deserves the merit of first worthily exhibiting legal medicine as a science. In France in 1609, under a patent of Henry IV., two surgeons were appointed in every considerable town to make examinations and reports in all cases of wounded or murdered persons. The application of the so-called hydrostatic test of Galen to cases of supposed infanticide, which had been sug-Rested by Harvey, was discussed in several disquisitions by Bartholin (1663), Swammer-dam (1677), Jan Schreyer (1682), and toward the close of the century by Bohn, in his treatise be Rmunciatione Vulnerum. In a later work Bohn treated of the office of the physician as expert in judicial tribunals. France produced during this time no very celebrated works on forensic medicine, but the Doctrine dts rapports en ddrurgie of Blegnv (1684), and the more useful book of Devaux on the same subject, are honorably mentioned in this branch of the science.

In 1722 Valentin! contributed to the literature of the science the Pandectm Medico-Legates. Between 1725 and 1747 were issued at Halle the successive volumes of the Systema Jurisprudential Medicae of Albertini This work was followed by the Institution Medicina Legalis vel Foremis of Tischmeyer, which was used for a long time as a handbook in the German universities, and formed the text of Ilaller's lectures, which were published after his death in 1782 and 1784. The Elementa of Plenck (1781) and the Systerna of Metzger (1795) are commended by writers of high authority. So too is the collection of Metzger's constitutions or opinions, many of which embody the results of his studies in mental disease as a branch of legal medicine. The Collectio Opusculorum, edited by Schlegel, and embracing upward of 40 dissertations by German authors on various topics, was one of the most valuable additions made during the 18th century to the learning of the science. In the latter part of the 18th century, infanticide was made the subject of elaborate research by Daniel and Ploucquet, among others, the latter of whom published an essay upon the evidences of respiration in new-born infants; and by Metzger, Portal, and Camper, of whom the last wrote upon the signs of life and birth in newborn infants, and upon the causes of infanticide.

During the same period the eminent French surgeon Antoine Louis, both by private dissertations and by his opinions pronounced before the tribunals, contributed to the illustration of some of the most difficult topics in legal medicine. Among the former are his memoirs upon tardy births, on the certain signs of death, on drowning, and on the mode of distinguishing between suicide and assassination in the case of a body found hanged. But his opinions, many of which are collected in the Causes celebres, present perhaps the clearest evidences of his genius. A valuable memoir upon death from blows or wounds was read by Chaussier at Dijon in 1789, and the next year he delivered there a course of lectures upon legal medicine. Shortly before the close of the century Fodere published Les lois eclairees par les sciences physiques, ou traite de medecine legale et d'hygiene piiblique. This treatise displays the entire system of the science. Dr. Parr published in England in 1788 the " Elements of Medical Jurisprudence." This book was a mere compilation from continental authorities, but was at the time the only English work upon the subject.

In the first year of the present century, the first lectures in Great Britain upon medical jurisprudence were delivered at Edinburgh by Dr. Andrew Duncan, and in 1806 the first professorship was established in the same city, and conferred upon Dr. Andrew Duncan the younger. The most important accessions to the science of legal medicine in recent times are those derived from studies of mental disease, and the application of the knowledge thus obtained to determining questions of legal responsibility; and from investigations into the nature and effect of poisons, and the mode of detecting their presence in the human body. The first systematic work of this century is the posthumous one of Dr. Mahon (1807), professor of I legal medicine at Paris. In 1808 Marc published a translation of the German work of Rose on medico-legal dissection, to which he added valuable original notes and essays. Fo-dere in 1813 issued a second and much enlarged edition of his treatise. Of a far higher character than any work which had preceded it was the Toxicologic generate of Orfila, which appeared in 1813-'14, and was followed some years later by his Legons de medecine legale, Orfila rendered the most eminent services to the science, and particularly in the department of toxicology.

The elaborate treatise of Devergie made still further advances alike in the theory and practice of legal medicine. Briand, Capuron, Biessy, Esquirol, and Marc are authors of learned treatises or of dissertations on single subjects. But any sketch of the French literature upon this subject would be incomplete without mention of the Annales d'Hygiene publique et de Medecine legale, a quarterly journal, which from its first appearance in 1829 to the present time has been supported by the ablest medical men of France, and is an invaluable repository of information on the various branches of medical jurisprudence. The Germans still maintain their high rank in this science. Schmidmuller, Wildberg, Gmelin, Remer, Bernt, Henke, and many others have made the most various and valuable additions to the learning of medical science and jurisprudence. The principal Italian authors of the present century are Tortosa, Martini, and Barzelotti. In 1818 Dr. Male produced the first respectable English work on forensic medicine.

More comprehensive and better in many respects than any which had preceded it, was the treatise of Dr. John Gordon Smith (1821). Two years after appeared the more formal and elaborate work, the result of the combined labors of a lawyer and a physician, Messrs. Paris and Fonblanque. Dr. Christi-son's works on poisons are of the highest excellence. Haslam on insanity, Hutchinson on infanticide, Watson on homicide, Gavin on feigned diseases, Taylor, Guy, and Traill, are authors of high eminence in their various specialties. Lectures upon medical jurisprudence were first delivered in America in 1804 at Columbia college, by Dr. James S. String-ham. In 1815 Dr. T. Romeyn Beck was appointed to lecture on the science in the western medical college, and not long after Dr. Walter Channing received a similar appointment in Harvard college. American authors have furnished some of the very best works upon this science. The well known work of Dr. Beck (12th ed., 1863) was pronounced by Dr. Traill of Edinburgh the best book on the general subject in the English language.

American editions of various English works, and the publication of the excellent treatises of Wharton and Stille, of Dr. Ray's book on insanity, of Elwell on malpractice, of the "American Journal of Insanity," and the "Journal of Psychological Medicine," maintain the high reputation of our country in its culture of medical science and jurisprudence. - The very general survev of legal medicine which is here proposed will exclude all notice of medical police or public hygiene, and will be exclusively limited to a brief review of the more prominent branches of the science. Following the division of Briand, the subject may be conveniently arranged under three heads: the first embracing those branches which concern the reproduction of the species; the second considering injuries to health and life, the different forms of death by asphyxia, and the nature and effect of poisons; and the third examining mental affections. - In the male, absolute and incurable impotence may arise from total absence, unnatural form, or paralysis of the organs of generation. Curable conditions may be the consequence of disease or sensual excesses, or of slight malformation which can be relieved by surgery.

Accidental and temporary incapacity may be caused by nervous or malignant fevers, particularly if they affect the brain and are accompanied by great debility, all affections of the head and spinal marrow, palsy, apoplexy, and the like diseases. This class of causes usually comes to be considered upon questions of contested paternity; for if it appear that any of these existed at the time of the child's conception, the presumption is strong against its legitimacy. In the female, malformation may render intercourse impossible. If it existed at the solemnization of the marriage and be incurable, it is sufficient ground for divorce. Female impotence may also be caused by diseases which may yield to medical treatment. In two instances familiar to the theory of the common law, though rare perhaps in its administration, medical testimony may be invoked by the courts upon the question of pregnancy: first, where a widow is thought to feign herself pregnant in order to supply a supposititious heir to an estate; and secondly, where a female condemned to death is supposed to be in that condition, for her execution will be delayed if she be quick with child. But in other respects, and particularly in relation to abortion and infanticide, the existence of pregnancy may he a significant fact.

In respect to the crimes of abortion and infanticide, and also with reference to civil cases, when questions of heirship are involved, it is important to consider the signs of a child's death before or during delivery. From the sound health of the woman, and the usual signs of a healthy pregnancy, nothing can be conclusively presumed respecting the life of the foetus; and on the other hand, though violence and those other causes which tend to produce miscarriage may and usually do destroy the foetus, yet infants sometimes survive all these. The signs of death during pregnancy are numerous, and yet equivocal. Auscultation is one of the surest means of detecting foetal life. After the birth, the physician can judge from the appearance of the body, from the condition of the flesh, from its color, from the condition of the umbilical cord and of the nones, whether the infant was dead or alive at delivery. The successive stages of foetal life, as they are marked by the size, weight, and development of the organs and' functions of the child, will throw much light upon the matter in question. In its latest researches science has found that the changes in the brain furnish an index of the general development.

Yet all inferences derived from the structure and dimensions of the foetus will be moditied and controlled by considering the age and vigor of the mother, her mode of life, and perhaps the climate in which she lives. All systems of law contain provisions respecting newly born infants. To succeed to property, according to the Roman law, the infant must be perfectly alive. The English law makes a like requirement. By the French civil code the child must be viable, or capable of life, in order to be capable of inheriting; and on the authority of the most eminent surgeons and jurists of France, life, or being born alive, means complete and perfect respiration. The viability of a child, that is, its capacity of life, conies then to be considered in questions of property, and of the division of inheritances; for a child which is declared by medical science to have been viable may be presumed to have lived, and so to have inherited. "It is now very generally conceded," says Beck, "that no infant can be born viable until 150 days, or live months, after conception.

The instances of exception to this rule are questionable; indeed, the survival of infants born at six, seven, or even eight months after conception, is by no means frequent." The criminal destruction of the foetus while still in the womb, generally described by its consequences as abortion, is more fitly named foeticide. (See Abortion.) The duty of the medical expert in cases of supposed foeticide is to determine whether the substance expelled from the womb be really the product of conception, and whether the causes of miscarriage were natural or artificial. - Infanticide is the murder of a child born alive. Here the medical examiner must address his inquiries first to the appearance of the body in order to determine whether it was born alive. If that be dear, he will seek to determine how long it lived, and the means by which it came to its death. These inquiries will naturallv involve an examination of the alleged mother. Proof that life has existed in the child may be derived from the effects of respiration upon some of the organs of the body.

In a child which has breathed completely and fully, the thorax will be found expanded and the diaphragm more or less depressed by the inflation of the lungs; but these signs alone are not of much value'. Inspiration will also have distended the lungs and increased their volume, and will have changed their color from the brownish tint of the foetal lungs to a pale red or scarlet color. After respiration the lungs become soft and spongy, and they crepitate more or less upon pressure. The hydrostatic test is often applied. Galen had taught that by inspiration the lungs are rendered specifically lighter, and in modern times the test was first applied by Schreyer in 1682 to cases of suspected child murder. In the course of experiments it has been found that the lungs may float from other causes than respiration, as for example from putrefaction and the artificial introduction of air. But, observing certain precautions, it may be certainly known to what cause the buoyancy is due. If, says Beck, with such precautions it be found that the lungs float in the water, as well with the heart attached to them as separate from them, and if when cut into pieces each fragment floats, then the proof is strong that the infant enjoyed perfect respiration.

Something may also be concluded, though not with much certainty, from the character of the blood found in the body, but more from the changes in the blood-circulating organs which are known to be wrought by the establishment of respiration, as, for instance, in some of the vessels and ducts of the heart, and in the arteries and veins of the umbilical cord. The separation of this cord, in the living child, is preceded by several stages of desiccation; and if this characteristic be present, its condition will afford evidence of the infant's age. To the validity of these indicia, so far as they tend to show the fact of life, it has been objected that the child may have breathed during delivery, and yet have died before it was fully born. It is replied to this, that the fact of breathing during birth affords the best presumptive evidence that the infant was born alive, and that the marks of any accidental cause of death will generally be discovered on inspection. More than that, respiration in such cases is commonly imperfect, and the objection will therefore have but little weight where the body presents the appearances which are induced by complete respiration.

If the examination lead to the conclusion that the child was born alive, the means of death must next be determined, and whether they were innocent or criminal. The omission to tie the umbilical cord, permitting fatal haemorrhage by its severed vessels, may be a cause of death. In such a case the body presents externally a singular paleness, and a peculiar waxy appearance. Internally is observed a loss of color in the muscles and viscera, and absence of the usual quantity of blood in the heart and blood vessels. Exposure to cold immediately after birth, want of proper nourishment, the infliction of blows and wounds, the thrusting sharp instruments into various parts of the body, are frequent modes of child murder. In cases of strangulation, suffocation, and poisoning, the indications of the cause of death are evident, and are suggested under the proper divisions of this article. It must be remembered also that accidental causes attendant upon birth, congenital disease, malformations or defects of internal structure, may deprive the child of life or render it incapable of living. The mother may have been overtaken by the pains of labor when alone and unassisted, and then there are many chances against the safe delivery of the infant.

Fainting or convulsions, which sometimes attend labor, may render her incapable of ministering to the first wants of her child; unskilful and imperfect ligature of the umbilical cord may produce death. An examination of the supposed mother has already been suggested. - In determining questions of legitimacy, the consideration of premature and tardy births necessarily arises. The ordinary period of gestation, derived from accurate data, is fixed at ten lunar months, or 280 days. It is admitted on high authority that this time may be exceeded, but it has been suggested that the apparently exceptional cases maybe explained by the fact of inaccurate computation. Still it is to be remembered that the human foetus is ordinarily expelled only when it has attained sufficient development, and that, as this may be delayed by disease or other causes, it is not strange that delivery may be for a longer or shorter time deferred. Whether a child born before the time expected is to be regarded as legitimate, has been already incidentally discussed. It has been seen that the best authorities deny that a perfectly natural child can be born in less than seven months after conception.

The absence or incapacity of the husband during this period, and all other causes which render intercourse impossible, tend strongly to prove illegitimacy of the child. Births occurring at 13 and even 14 months after an alleged coition have been sometimes claimed to be legitimate. This topic of protracted gestation has been abundantly discussed by medical writers. It must suffice here to say that, though the theory seems to be ably opposed by many, it is yet favored by a majority of the authorities, among whom are included Bacchias, Haller, Petit, Fodere, Capu-ron, Orfila, and others of almost equal eminence. It may be added that, of the cases cited in support of this theory, the best authenticated are those in which the ordinary period of gestation was exceeded only by three or four weeks. - When a person is found dead under circumstances which render the cause of death doubtful, the medical expert may be called upon for an opinion whether death resulted from natural causes, or from violence; and, if by violence, whether that was self-inflicted or by the hands of an assassin.

Under this division of our subject we shall notice some of the more usual and characteristic phenomena observed in cases of death by blows and wounds; by asphyxia, considering here drowning, hanging, and suffocation; and finally, by poisons. The appearances in the body which are caused by effusions of blood will attract the early attention of the examiner. When a blow or contusion is sufficiently violent to rupture blood vessels, the effused blood spreads into the cellular tissues and forms ecchymosis. The intensity and graduation of color in these spots give clear indications of their cause, and the freedom of the haemorrhage shows that they were produced during life. Ecchymosis is named traumatic when, as is usually the case, it proceeds from external causes, and spontaneous when it is the effect of internal violence. From this must be distinguished the post-mortem appearances caused by suggillation. This is the term applied to the determination of the blood, merely as an effect of gravitation, into the lower lying portions of the dead body, and into the capillary blood vessels, and not into the cellular tissue.

Ecchymosis may be imitated on the dead body within a short time after life is extinct; but very violent blows inflicted then will produce only the same effect as slight contusions during life. The body may plainly show, or dissection may disclose, that death was caused by wounds, that is to say, in the language of legal medicine, by a lesion of any part of the body. It may be. remarked in passing that, in law, a wound means a breaking of the skin, at least, by the application of extreme violence. A division of the cuticle alone is not sufficient. The true skin must be penetrated, though there be no effusion of blood. In surgery, a wound means a solution of continuity, or disruption, in the fleshy parts. The first inquiries of course will be whether the wounds discovered were self-inflicted, or resulted from accident, or were given by a homicide. The position and direction of the injuries will be noted. The presence of many wounds argues violence by another hand than that of the deceased. The suicide generally directs the hurt to a single vital point. A wound made by a cylindrical and pointed instrument has distinct angles. A cut is larger than the cutting edge, and in the living body is always accompanied by some effusion of blood.

A wound by a perforating instrument is generally smaller than the instrument which inflicted it. The entrance made by a ball is distinguished by the regular roundness and depression of its edges; the exit wound is torn and ragged. The former is also larger than the latter. The spiral motion of a rifle ball causes a more ragged wound than that of a ball from a smooth-bored arm. A single round wound can be produced by a shot charge only when it is fired at a distance of 10 or 12 inches, and then the injury is not the same as that of a ball, but is more extensive and more serious. The examination of spots supposed to be made by blood may lead to important discoveries. Blood washed from linen into water imparts to it a deep red color; boiling produces a muddy brown precipitate which is to be subjected to chemical tests. In fresh blood the microscope reveals the presence of red flattened disks, which are the blood disks, and among these, more rarely, the rounded colorless lymph globules. These latter may still be observed under the microscope in the water in which dried blood has been softened; the blood disks are less easily obtained. It is often a question for the medical expert, when disease has succeeded to the injury, whether death resulted from the one cause or the other.

If malignant or inflammatory symptoms follow upon slight wounds, the inference is ordinarily not difficult that the injury was not the cause of death. The habitual use of intoxicating liquors tends to induce a diseased condition of the system, and in a state of actual drunkenness the vessels of the body are in that condition in which an external injury is apt to produce rupture, and a less violent blow will cause it than would otherwise be required. Legal responsibility rests on the clear and direct consequences of the injury inflicted. This principle must always be borne in mind. For disease, though developed in organs far from the seat of the wound, may yet be its immediate result; as, for example, injuries on the head may promote a deposition of pus in the lungs, or give rise to abscesses of the liver; and on the other hand, death may result from improper medical treatment, or from the negligence or excesses of the injured party himself. (For the subject of malpractice, see Physician.) Though external marks fail, the skilful anatomist may discover upon dissection internal signs of mortal injuries. Blows or wounds upon the surface of the body may possibly rupture the heart.

Ruptures of aneurisms may be produced by the excitement of passion, and laceration of the spleen or liver by a fall or other sudden external violence. Death from starvation is characterized by distinctive phenomena. The body is extremely emaciated, and, even though death were recent, exhales an acrid and fetid odor; the eyes are red and open, the tongue and throat dry, the stomach and intestines empty, and the gall bladder distended with bile; the blood vessels and internal organs are comparatively destitute of blood. - "When life has been destroyed by the inhalation of noxious vapors, as for instance of carbonic acid or sulphuretted hydrogen gas, the head and face are found to be swollen, the eyes protruded, and the tongue fixed between the teeth. The face, if observed soon after death, may be pale, but generally soon becomes livid. The blood vessels of the bead and lungs and the right vessels of the heart are tilled with dark fluid blood. Pure carbonic add gas is irrespirable, and inhalation of it causes death rather by asphyxia than by poisoning. When mixed with atmospheric air, 20 per cent, of this gas is very promptly fatal to hfe, and even a smaller "proportion may produce the same result. Death from asphyxia is caused in various ways.

When respiration is checked by mechanical compression of the organs which perform that function, or when it ceases either from want of air, as in cases of suffocation and strangulation, or from failure of vital air, and the inspiration of mephitic or deleterious gases, death is caused by asphyxia. Properly speaking, death ensues in those cases from non-aeration of the blood. It is preceded and accompanied by marked phenomena, more marked, and evident in proportion to the rapidity with which death advances. In a violent struggle for breath, the eyes become distended, the veins swollen, and the face is fully suffused. On dissection, the pulmonary vessels and the right auricle and ventricle of the heart are found charged with blood, the liver, spleen, and. kidneys are gorged, and the lungs expanded. In cases of less violent death, where, for example, it is brought about by inhalation of noxious gases, these appearances are less strongly marked. - Hanging sometimes causes death by producing congestive apoplexy, the pressure of the cord preventing the return of blood from the brain, while it does not check the circulation by the intervertebrals; but more frequently the destruction of life is due to asphyxia. Luxation or fracture of the cervical vertebras speedily causes death.

The signs of strangulation are a livid depressed circle upon the neck, made by the cord; the face is distorted; the eyes are open and protruded; the face, shoulders, and chest swollen. The ec-chymosis produced by the cord is an important sign, for, as has been already observed, ecchymosis is possible only when contusion of the tissues takes place in the living body; yet in inferring the mode of death it is to be remembered that as death in hanging may suddenly result from luxation, the cord may have had no time to act on living tissues. The condition of the genital organs also affords very important proof of death by hanging. The color of the countenance is also to be regarded. If the trachea or larynx was alone compressed, the face is pale; but when the veins of the neck were pressed, as by the cord, and the heart continues its action for some time, the blood is propelled into the head and causes suffusion of the face. The question may arise whether, if the deceased came to his death by hanging, it was his own work, or the work of a homicide. An examination of cases of suicide has shown in a large proportion of them the absence of ecchymosis; and this because from the employment of less violence the contusion of the neck was less.

Fracture of the vertebras of the neck is often caused in execution by the fall of the body or even by force which is sometimes applied by the hangman. But luxation is of course not conclusive evidence of homicide. An examination of the position of the body and of the objects which surround.it, of its elevation above any possible support, and any marks which show resistance, must be made in all suspected cases. In strangulation, in its ordinary sense, death results not from fracture of the vertebra), but from interruption of respiration. This is a rare mode of suicide, and when appearances indicate that it was the means of death they raise a violent presumption of assassination. Because death ensues from interruption of the breath, the mark of the cord must be quite distinct, and is rather horizontal than oblique. Bruises of peculiar form around the neck may show that strangulation was effected by the hands. It is impossible that these should have been made by the suicide, because the hands lose their power as insensibility advances.

But in cases of hysteria, apoplexy, or epilepsy, the sufferer may in his agony have pressed the hands to the throat, and in this way have made the marks which give rise to a suspicion of murder. - Obvious and distinctive marks are, says Dr. Chris-tison, rarely present in a case of death by suffocation. They are the less evident as death is the more rapidly induced; for if there be no time for the accumulation of blood in the venous system, there will be no enlargement of the pulmonary vessels, no turgescence of the veins, and no discoloration of the skin. In the cases which occurred in the Champ de Mars in Paris in 1837, of suffocation by pressure in the crowd, when death was probably caused by respiration being incomplete, and was long deferred, the bodies of the dead exhibited peculiar appearances. Their faces and necks were of a uniform violet tint, spotted with blackish ecchymosis, and in some instances blood and froth oozed from the mouth and nostrils. - As in hanging, so in drowning, life is destroyed by different modes, sometimes by suffocation, or rather by the asphyxia which that causes. This is the most usual form of death by drowning. Another form is that of syncopal aspyhxia.

In these cases, the coldness of the water, or perhaps intoxication, throws the system into a condition of nervous inaction, and the body presents only the appearance of simple asphyxia, paleness of the body, no froth in the trachea or bronchi, and but slight disturbance of the internal organs. Still another cause of death is apoplexy from cerebral congestion. A drowned body usually presents general paleness of the skin, yet the face will be discolored if death was preceded by long-continued struggling. It is to be remarked that upon exposure of the body to the air, discoloration very speedily ensues. The eyes may be found half open, attended by dilatation of the pupils. These signs, as also frothing at the mouth, may proceed from other violent means, but still are strong proof of drowning. Of the internal appearances of the body may be mentioned a fulness in greater or less degree of the blood vessels of the head and of the right side of the heart. The congested condition of the brain varies with the proximate cause of death. If that was apoplexy, it would certainly be present, but rarely or not at all in the case of syncopal asphyxia. The blood of the drowned is generally found fluid.

The existence of froth in the bronchi is perhaps not a conclusive proof of the mode of death; but it is certainly the result of vital action, and so may be a valuable sign in conjunction with others to prove that life existed when the body was immersed. The presence of water in the stomach is merely accidental, and is not very nearly connected with the cause of death. As upon high authority it is asserted that water cannot pass into the stomach after death, its presence in it may be in certain instances significant. When death arises from obstruction of the breath by water, and not by apoplexy, some of the fluid enters the lungs with the last efforts of inspiration. Yet neither the fact that it is found there, nor its quantity, can be regarded as proving conclusively that death took place in consequence of immersion; for under favorable circumstances water may penetrate into the lungs even of a dead body. - Fodere defines poisons as those substances which are known by physicians to be capable of altering or destroying, in a majority of cases, some or all of the functions necessary to human life. The intent with which such a substance is administered enters of course into the legal conception of a poison. Poisons may be ranked under the two great divisions of irritant and narcotic.

To irritant poisons belong the corrosive acids and some of their compounds, the alkalies and their salts, the metallic compounds, and the vegetable, animal, and mechanical irritants. The characteristic of these poisons is the inflammation which their application excites. Their most notable effects upon the human body are heat, irritation, or singular dryness in the oesophagus, accompanied by a sensation of strangling; pain in the stomach and intestines or in the region of the kidney-, followed by strangury; evacuations both by vomiting and at stool, convulsions, faintings, cold sweats, and an irregular thready pulse. There is usually a retention of the intellectual faculties until the disease approaches a fatal termination. Narcotic poisons, on the other hand, which include many vegetable substances, prussic acid and its compounds, and the narcotic gases, nitrogen, carbonic acid and oxides, oxygen, hydrogen, and others, arc distinguished by the disorders which they produce in the nervous system. They are defined by Ortila to be those which cause stupor, drowsiness, paralysis, or apoplexy and convulsions.

Among their" usual effects, in the various stages of their influence upon the body, may be mentioned numbness, coma, and sometimes delirium, cold and fetid perspiration, swelling of the neck, face, and sometimes of the whole body, dilatation of the veins, protrusion of the eyes, general prostration, chilliness and paralysis of the extremities, and, just preceding death in some instances, pain and convulsions. The narcotic-acrid poisons produce combinations of several of these symptoms. The effects of poisons differ widely in different persons, and are more or less distinctly marked according to the form, whether solid 01 liquid, in which the poisonous substance is administered. The symptoms are naturally varied too by the condition of the system, particularly of the stomach, when the poison is taken. ■ It may be added here that the effects of poisons may be closelv imitated by certain diseases, as for example cholera. Rupture of various intestines, of the stomach, the duodenum, or the uterus, may produce symptoms similar to those of irritant poisons. In seeking for the evidences of poison in a dead body, the first inquiry is as to the nature of the substance taken.

It is a distinctive feature of the irritant poisons that they excite inflammation, in greater or less degree, in every part to which they are applied, and internally corrosions or perforations where the poisonous matter rests longest. The intlammation varies in extent and intensity. It is usually observed in the mouth, throat, and stomach, but may reach through the whole length of the digestive tube. The membranes are of various degrees of redness, sometimes accompanied by dark patches of extravasated blood, and sometimes also by ulceration. The traces of narcotic poisons are not so evident. Dr. Christison says even that the marked appearances which they leave are insignificant. Certainly, it is not characteristic of this class of poisons, as is often supposed, that they induce putrefaction, or that the blood remains fluid. Often, however, the veins of the head are found gorged with blood, the lungs bear black and livid spots, and their texture is less dense. These same changes, both in the brain and in the nature of the blood, are produced by the narcotic-acrid poisons. For the purpose of charging innocent persons with murder, poisons have been in some instances injected after death.

Orrila found that he could not reproduce in the dead body the appearances manifested by the living tissues. In the latter case, inflammation in graduated stages of intensity always attends the injury. But in his experiments there was always a perfectly defined line of demarcation between the points to which the poison was applied and those adjacent. In examination of the stomach, it is to be remembered that the vascularity or redness of this organ may arise as well from natural causes as from the influence of poisons. This appearance occurs, says an eminent author, in every variety of degree and character, under every circumstance of previous indisposition, and in situations where the most healthy aspect of the organ might be fairly inferred. Nor are marks of poisons to be confounded with those discolorations which may be produced by the liver and spleen. Ulcers and perforations have sometimes been wrongly attributed to the effects of poison. What is called the self-digestion of the stomach has often been mistaken for poison. In this condition of the organ its coats are rendered thinner and transparent, and sometimes the destruction of them advances even to perforation. These must, be distinguished from those which are caused by corrosive poisons.

The latter have clearly defined edges, and thick as the thickness of the coats which are pierced. these margins, too, are usually of a peculiar color, according to the poison employed; for example, yellow with nitric acid, brown or black with sulphuric acid and the alkalies, and orange with iodine. Finally, in a case of spontaneous erosion, there is generally a remarkable whiteness of the inner wall of the stomach; but in a case of poisoning there must be unequivocal signs of inflammation or of irritation. - In reference to the application of chemical tests, it may be remarked, that poison may be absorbed or decomposed, and in such cases it may be found by boiling the stomacli and intestines, and subjecting the fluid to proper tests. Poisons which remain in the dead body may be affected by the chemical changes involved. By the ammonia disengaged during decay acids may be neutralized; and by the action of the animal matter the mineral salts may be decomposed. Soluble poisons, as oxalic acid, disappear; arsenic, opium, cantharides, and strychnia are not essentially changed. Among the most important of the irritant class, or usually arranged in this class, are arsenic, the salts of mercury, lead, copper, and some other metals; sulphuric, nitric, oxalic, and some other acids.

Of the narcotic class may be mentioned opium, prussic acid, strychnia, and the oils of cedar, tanzy, and savin; but some of this class also cause nervous irritation. - Insanity, in all its forms, is an important topic of medical jurisprudence. (See Lunacy).