Certain substances are possessed of an affinity for specific parts of the system,‡and very often regardless of whatever route may be selected for their admission. After the hypodermic injection of emetina, it may be found in the contents of the stomach, or in the matter vomited. § Croton oil effects a specific action on the intestinal mucous membrane, as when injected into a vein it has caused death and the whole length of the intestines has been found in a state of inflammation.|| Cubebs and copaiba act specifically upon the genito-urinary organs, and increase the quantity of urine, to which they communicate a peculiar aromatic odor. Their operations are not confined to these organs, they being stimulants of the mucous surface generally. || They both produce a rash. From the cubebs, it is of an orange-red color, and more distinctly papular, each spot being smaller than that produced by copaiba; it shows also a more decided preference for the trunk of the body than lor the extremities.¶

The constitutional effects of arsenic are twofold, acting upon the blood and the skin. Its action on the blood arises from its property of direct combination with the blood globules. This combination is made at the expense of the oxygen, arsenic taking its place.** When administered before death, it has been carried into the antehepatic portion of the vascular system, then it arrives in the liver, where it accumulates, for two reasons: first, it is carried there directly' second, after its diffusion throughout the system it returns to the liver, because this gland is the eliminating organ for arsenic and the metals.* In many cases, when the recognition of the poison in the blood fails, the poison can be detected, unaltered, in the secretions, such as the saliva, or urine.† It likewise may be found in the nails, which is one way by which the metals are eliminated. A brownish tinge of the nails has been observed in healthy subjects who take sulphurous baths. From large doses of arsenic, it may be found in the hair and bones. Ergot has its election for the involuntary unstriped variety of muscular fibre.:}: The uterus, especially, in the gravid state, is the principal example of this variety of muscular fibre, and it is on this that its effects are most marked and best known; but we have it also existing in the bladder, the gullet, the stomach, the intestinal canal, the bronchial tubes, the ducts of many glands, the iris, and which is perhaps still more important, in the middle coat of arteries. Both ergot and strychnine are potent agents on the motor system and act by giving force. But ergot addresses itself to the motor system, or organic life, to the smooth fibres which animate it; strychnine on the contrary to the medullary portion.*

*Prof. R. T. Edes. ‡Prof. Adolph Gubler. ‡Prof. Rudolph Virchow. §Prof. R. T. Edes. ¶'hill and Cooper.

||Waring.

**Dr. J. C. Cleland.

Opium has its elective seat in the encephalon, and has an almost exclusive action on the nervous system. Aconitine acts on the expansion of the nervous system. Phosphorus addresses itself to the nervous system. Aconite to the division of the 5th pair. Iron and the salts of potash to the globules of the blood, aloes to the rectum, belladonna to the iris, digitalis to the heart, ipecac to the mucous membrane. The neutral salts in general will provoke the salivary glands.*

The chloride of gold and soda, somewhat like mercury increases the secretions, especially the saliva, though without stomatitis. || Of the sialagogues, which act immediately on the salivary organs we have the armoracia, calamus, mezereum, pyrethrum, tabacum and zingiber.¶ Jaborandi exercises its force, not only on the glandular system, but on the skin, as a powerful diaphoretic. Alum is absorbed into the system, and has been detected in the liver, spleen and urine. Its astringent influence is chiefly directed upon the mucous surface. The bromides, antagonistically to strychnine, show an elective influence on the spinal cord. The physiological action of convallaria is to stimulate the vagus, which it afterwards paralyzes. The action of conia may be exerted upon the nervous system, and not on the muscles.**

There are several cardiac remedies of differential effects. Of those of a tonic nature, digitalis is deemed first in power, after which bromide of potassium; next in order, convallaria and caffeine, †† Convallaria has a decided tonic action on the heart.* The sphygmographic tracings show that convallaria not only diminishes the number of pulsations, but that it does this while augmenting the amplitude of the contractions. It is this period of slowing and augmentation of amplitude that gives us the appropriate name of the "therapeutically useful period" of convallaria, and when you compare this "useful period" with that which belongs to digitalis in like doses, it is found that the superiority is to be assigned to convallaria.† From the standpoint of its action on the human heart, it is one of the most powerful diuretics known, † and ranks before digitalis.*

*Prof. Adolph Gubler. ‡ Dr. A. Meadows

||Prof. R. T. Edes. **Waring.

†Prof. L. Herman.

§Waring.

¶ Prof. R. Dunglison.

††Dujardin Beaumetz.

It is agreed at the present day not to give the preparations of digitalis continuously, but to renew this medicine again after a suitable interval. It is during this period of suspension of the foxglove that convallaria can be employed, taking care, of course, not to attribute all the diuretic effects thereafter obtained, to this medicine, for the action of digitalis on the kidneys is prolonged for some time after its administration ceases. †

Caffeine is one of the best tonics of the heart in the last stages of cardiac affections, and will render more service than digitalis.† In moderate doses it diminishes the pulsations while it augments the vascular tension. In large doses it produces toxic effects, the heart beats are accelerated, and become irregular, the caffeine having become a poison. Caffeine manifests through its influence on the heart, a decided elective force on the kidneys even when in a badly damaged condition.† In the aged and in the asystolic period - a period of cardioplegia,‡ when there has been exhausted the remedial powers of all the cardiac tonics, there may still be obtained signal success with caffeine. †

Adonidine, like digitalis, has the same action on the heart without being attended with any danger of cumulative effects.† Sparteine has a special effect in regulating the action of the heart. Cactus grandiflorus and cereus bon-plandii each act as a cardiac tonic and nervine, § and are indicated in weak heart from nervous irritation or exhaustion and valvular deficiency. || The latter can be used to advantage in both functional and organic affections of the heart. || Euphorbia pilulifera addresses the respiratory and cardiac centers alike, but leaves intact the other organs, and seems to be eliminated by the liver. ¶ The essence of turpentine, of cajaput, of eucalyptus, direct their influence upon the respiratory passages, or on the skin. ‡

To modify a cough, recourse must be had to the volatile narcotics, which will act first on the nervous system, and locally where they are eliminated. To act on a catarrh of the urinary passages, there will be indicated analogous substances, but having different qualities. Thus will be employed precisely all the essential oils which are rapidly resinified, and which, passing to the state of oxides, combined with the acids and become true salts; they will be administered in preference, because they will pass, in large part, by the urinary passage.*

*Prof. See.

*Dujardin Beaumetz. ‡Gubler.

||Dr. R. E. Kunze. ¶Therapeutic Department of Parke, Davis & Co.

†Giraud and Lebland. §Dr. Austin Flint.

The elective force of alcohol, ether, and chloroform, is to the brain. They all possess the property to dissolve fatty bodies. When poisoning by these substances has taken place, they are found in large proportion in the brain, exactly as if they had come in contact with a substance with which the}- have a species of affinity. This fact is repeated by the alkaloids.

A therapeutic election to some part of the animal economy may be assigned to every medicinal agent in the Materia Medica. This election of organs, by remedies administered, is mainly due to chemical affinities that may exist between the medicines and the different histological elements of the human body, either in a healthy or morbid condition.

This principle is not confined to medicines only, but applies with equal force to food. Hence the use of one article as a diet will never be sufficient if used for a long time to maintain health. Every article of food or medicine possesses each a chemico-physiological element of* its own, which it surrenders in its place of selection. On these grounds, the line between food and medicine is not easily established. Those who decry medicine as an evil, and medication as a struggle against nature without any substantial good, might make the same deduction on the use and abuse of food.