Monster, a term limited by Isidore Geof-froy Saint-IIilaire to the complex and grave congenital anomalies of conformation, disagreeable to the sight, rendering difficult or impossible the accomplishment of certain functions, and producing a disposition of organs very different from that ordinarily presented by the species, whether animal or vegetable, involving change in the form, structure, volume, position, and number of parts. This definition excludes simple vices of conformation, such as bare lip, club foot, fissured palate, gigantic and dwarfed stature, albinism, and hermaphroditism. The phenomena of monstrosity were not examined in a philosophical spirit until the early part of the present century, when the sciences of comparative anatomy and embryology could be brought to their explanation; the principal workers in the field at this period were the elder Geoffroy Saint-IIilaire, Serres, and Meckel. The history of monsters, or teratology, is a science in itself.

In the fabulous period of this science, ending about the beginning of the 18th century, monsters were regarded as exhibitions of the creative power of God, as proofs of his anger and the signs of some approaching public calamity, or as the work of demons; and as such, by the old Greek and Roman laws, they were at once put to death; even as late as the 17th century they were either destroyed or shut up from human sight. In the first half of the 18th century the causes of monstrosity were zealously sought for, and from the time of Haller the science made rapid progress. - Many forms of monstrosity are embryonic conditions rendered permanent beyond the normal period, thus forming a series comparable to the ages of the foetus and to zoological divisions of ani-mals; others seem to be formed by excess of growth, according to the theories of original excess of productive power or eccentric development of the vascular system; double monsters, whether partial or complete, are united by homologous surfaces, side to side, back to back, or face to face, each internal organ of one having a corresponding organ in the other; and the laws regulating monstrosities, whether by excess or defect, are intimately connected with those presiding over normal organizations.

It is true, as Goethe says, that "it is in her monstrosities that nature reveals to us her secrets.1' Isidore Geoff roy Saint-Hilaire (Histoire des anomalies, etc, 3 vols. 8vo, Paris, 1832-'6) makes the two classes of single and compound monsters, which he divides into orders, tribes, families, and genera on the Linna3an zoological plan; in the first class he places all such as have the elements of only a single individual, and in the second those which have the parts, complete or incomplete, of two or more individuals. In the first class he makes three orders: A. Autosites, or such as are capable of sustaining life, sometimes extra-uterine, by their own organs, having a heart, lungs, almost all the digestive organs, and a portion at least of the head, most of the body remaining symmetrical and nearly normal. This order contains four subdivisions or tribes: I., in which the limbs are modified by deficient development or by fusion, or are absent; II., in which the viscera of the trunk are more or less seriously displaced and external, the limbs normal, incapable of extra-uterine life; III., in which the principal anomalies are in the cranium and brain, the modifications of the face and limbs being of secondary importance; the brain is deformed, incomplete, partially or wholly outside the cranial cavity, or even entirely absent, with corresponding deficiency in the arch of the skull; this includes an extensive series both in man and animals, among others the so-called anencephalous foetuses, all incapable of life beyond a few hours or perhaps days; in some the spinal canal is largely open, and the spinal cord as well as the brain absent; IV., in which the face is more deformed than the cranium, the nasal apparatus being atrophied or displaced, bringing the eyes near together, or the central region of the face so deficient that the ears are joined on the median line; this includes the one-eyed monsters, like the fabulous Polyphemus, and rhinencephalous foetuses; all these die speedily from the imperfection of the brain.

B. Omphalosites, living a merely vegetative life ceasing with the separation from the parent, many of the organs being absent and the existing ones very imperfect with abnormal and unsymmetrical forms; these include the parencephalous and acephalous foetuses, the former having some traces of cranium, but no heart sufficient to circulate blood, and the latter destitute of head except the merest rudiments, often having neither neck nor chest, and but few of the abdominal organs; they never reach the full term of gestation. 0. Parasites, including the imperfect products of conception commonly called moles; they are irregular in form, composed principally of bones, teeth, hairs, and fat, having no umbilical cord, and implanted directly on the parent organs, where they live a vegetative and parasitic life; in most cases these appear to be a deformed and abnormally developed placenta, with a few remains of the prematurely dead embryo; they have been found attached to the uterus and the ovaries, and the gestation has usually been much prolonged, even to years, some of the second teeth having been seen in their substance. - In the second class, or that of compound monsters, the double ones he divides into autositaires, in which the two individuals present the same degree of development, each having an equal share in the life common to both, a union of two autosites; and parasi-taires, composed of two very unequal or dissimilar individuals, one complete and the other imperfect, and the latter capable of living only at the expense of the former.

The tribes of the autosiiaires are: I. That in which the individuals are united only in a single region, the duplicity being complete in every other part. This tribe is naturally subdivided into two families, according as the umbilicus is double or single; in the former belong the double monsters united by any portion of the trunk or head, like the famous Hungarian sisters, Helen and Judith, joined back to back by the thighs and loins; these were born in 1701, and lived to their 22d year; they had neither the same temperament nor character, and Helen was larger, better looking, more active, intelligent, and gentle than her sister; they were very fond of each other, performed some physiological acts in common and others separately, and were sick and died together. Two black children, called the Carolina sisters, Christina and Millie, united by the lower part of the backs, have been exhibited in various parts of this country and Europe; in 1869, when they were 18 years old, they were apparently in perfect health. A lull description of them is given in the " Boston Medical and Surgical Journal" for July 8, 1869, from which it appears that the hips are so far separated that on one side two fingers can be passed in between them, there being only a crease on the other side.

The call to evacuate the bowels and bladder is simultaneous, and the intestines must therefore unite not far above their termination; there is a single anus and rectum between the anterior limbs, and the two urethral orifices and vaginas open into a common vulva. The mammary development is good, though the chests are considerably deformed from spinal curvature; menstruation is regular. If hunger and thirst be felt in both at the same time, it must be through nervous connections. They are two individuals, psychologically, morally, and legally; one may be awake and the other asleep; their general health is good, the weight being 170 lbs., about equally divided between them; their expression is cheerful, manners agreeable, and intelligence above the average; they sing together with good effect. They are inclined to rest on the back legs, and walk upon these, or upon all four, moving sidewise; the front legs are a little the shortest, from the elevation of the front hips from spinal curvature; they can walk rapidly, and even waltz.

They are united by the sacrum, and probably by the lower lumbar vertebras; both feel a touch upon the lower limbs, indicating that the sensory nerves, from the posterior columns, mingle at the lower part of the spine; but the motor nerves, from the anterior columns, are so distinct that one cannot move the limbs of the other. (See Aimales dliygiene piiblique, Paris, April, 1874.) To the family with a single umbilicus belong such as are joined in the hypogastric and sternal regions, front and sides of thorax, and sometimes even by the neck and jaws. Among those united by the xiphoid region of the sternum were the Siamese twin brothers, Chang and Eng, having a single urnbilious in the centre of the moderate-sized con-neoting process. They were born in 1811, were exhibited in most parts of Europe and the United States, and died, within a few hours of each other, in North Carolina, Jan. 17, 1874: each was married, and had several children, none of whom were monsters. They were physiologically distinct, having different forms, strength, tastes, and dispositions; their phvsical functions were performed separately; the sickness of one did not affect the other; hence there could not have been any free interchange of circulations.

In the connecting ensiform cartilage, the post-mortem examination showed that the band contained four peritoneal pouches, two of which met and overlapped on the median line, and that their livers and hepatic vessels communicated, though not freely, indicating that any attempt during life to separate them would probably have proved fatal; whether, had there been time and opportunity, the separation of the living from the dead would have been fatal, may admit of doubt. Chang died first, probably of cerebral clot, during the night; when Eng awoke and found his brother dead, his fright and the consequent nervous shock, acting on an enfeebled heart, produced a fatal syncope. lucre was a region of common sensibility in the median line of the band. Though these lived to the age of 68 years, in the last named members of the group the anomaly is generally incompatible with extra-uterine life. Tribe II comprises monsters in which the individuals are distinct at the pelvic extremity, but connected in the head and sometimes in the whole supra-umbilical region. In one family the bodies are united from the umbilicus upward, with the head more or loss completely double, in some with the two faces directly opposite; as far as known, this deformity is incompatible with life.

In another family the trunks are joined above the umbilicus, with a single head bearing but few marks of duplicity, and with two or four thoracic limbs; both these families occur in man, but the latter very rarely. Tribe III. includes such as have the head double, but the trunks more or less united into a single body and two lower extremities; sometimes the bodies are distinct from the umbilicus upward, with generally a rudimentary third lower limb; in others the heads are united behind, but show two faces in front. In the parasitaires the smaller and less perfect individual may be attached near the umbilicus, or very far from it, and may be reduced to a mere head without body; in some cases the monster seems a single body, with supernumerary jaws, portions of the head, or extremities; and in the least perfect of all the accessory growth is included within the principal body. The parasitic growth, from its small size, does not interfere with the birth, and such monsters have not only lived to be adults, but have become parents of well formed offspring.

Most authors deny the existence of triple monsters, but Geoffroy Saint-Hilaire admits it, regarding the quadruple and quintuple cases as fabulous. - Considering the whole number of births, monstrosities are rare; after man they are most common in the hog, ox, cat, sheep, dog, and chick. Many, if not most, monsters give no indication of anomalous formation in the course of gestation, and they are most frequently born of mothers in good health and who have previously had normal children; females which bring forth twins have been found most liable to produce monsters, the separate amnions of each from contiguity favoring the confusion or blending of parts; the birth is usually premature, though sometimes long after the natural time.The hereditary transmission of monstrosity is very rare, even when the reproductive functions are unimpaired. The female sex seems to predominate, taking the whole range of monsters. Monstrosity is more common and extraordinary in the vegetable than in the animal kingdom, from the easier derangement and displacement of parts; yet even here it is subject to and explicable by the laws of normal vegetable growth; some botanists consider double flowers and other similar products arising from peculiar culture as monsters, and such as these are perpetuated by seed.

Monstrosity may be due to an absence of formation; to an arrest of development, an embryonic structure remaining permanent; to an excess of development; and to a union of parts, more or less normal, belonging to different individuals. Prof. J. Wyman ("Proceedings of the Boston Society of Natural History," 1867), in a paper on symmetry and homology in limbs, draws attention to the analogy between symmetry and polarity, illustrating his remarks by figures; he thus explains both normal and abnormal development, and the various kinds of double monsters. Though it is impossible to admit the action of slight causes, of momentary continuance, popularly believed to be connected with monstrous or imitative growths, still the artificial production of variously deformed and imperfect chicks by the shaking, or malposition, or unnatural treatment of eggs, shows that appreciable external causes may occasionally be satisfactorily traced; it is now generally conceded that prolonged unfavorable circumstances during pregnancy may lead to monstrous growths. - See the works quoted by Geoffroy Saint-Hilaire, and the papers of G. J. Fisher, M. D.. in the "Transactions of the New York Medical Society " (1865-'8). (See Teuatology).

The Siamese Twins.

The Siamese Twins.

V. Vena cava. V. P. Vena porta, a. Upper hepatic pouch of Chan?, probably continuous during fietal life. b. Peritoneal or umbilical pouch of Eng, c. Lower peritoneal or umbilical pouch of Chang. d d. Connerting liver band, or tract of portal continuity, e. Lower border of band .f. Upper border of band. - There was also an upper hepatic pouch from the liver of Eng not represented, as it was not discovered till the organ was removed.