There is no part of therapeutics of greater interest than the investigation of the relative effects of homogeneous and heterogeneous substances introduced into the general system. Each class appears to be governed by laws of its own, in which there is no deviation, unless in the former very large doses are given, when characteristic effects are had, and then the action is in a measure, similar to that of heterogenic agents.

Such is the importance of this subject, that it is a matter of surprise that it heretofore has received so little attention, and has not already become the basis of a scientific system of practice.

To present this subject in its proper light, it would be necessary on the one hand, to give the analytical composition of all parts of the human body, and on the other, to divide medicine into three classes: the homogeneous, heterogeneous, and a compound of the two. A therapeutics on this basis would be strictly scientific, and would pave the way to reach a better knowledge of structural lesions - the heterogenesis of the animal body.

It is not through its mineral or vegetable nature that a substance acts, but whether it may be of a homogeneous or heterogeneous nature as regards the organism.a Thus, the soda salts should be accepted with facility by the organism, as they exist in all the tissues in great abundance.b

It may be held as a general rule, that medicaments are ejected with so much the more rapidity, as the more they differ from the principles which normally constitute the organism. Thus, the potash salts, more heterogeneous in the blood than those of soda, are tolerated with greater difficulty in this liquid, and are sooner ejected from the economy.a

The homogeneous substances can be tolerated in pretty large quantity; it is only when the dose is enormous that they begin to be eliminated.

Much chloride of sodium can be injected before it manifests its presence by an excess of chloride in the urine, but a moment arrives when its excess in the system will be shown by the passage of a larger quantity in the urine. It is the same with sugar.a

If you wish to produce effects through the difaprof. Adolph Gubler.

b6Foucroy.

fusion of the drug in the economy, and particularly alterative effects, that is, if you wish to modify in a slow, sustained manner the living economy, it is necessary to employ substances resembling as much as possible those normally present, and to employ them in small repeated doses for a considerable period of time. It is possible, no doubt, that with heterogeneous substances employed in very small doses, you may find sufficient tolerance to produce metatropic effects; just as with large doses of homogeneous substances you can determine topical effects on the emunctories. But the reunion of these two conditions - a heterogeneous substance in very large doses, to produce topical effects; a homogeneous substance in very small doses, to produce general and alterative effects on the system - it is necessary, if possible, to realize. Thus, for instance, mercury if employed as iodide of mercury, will necessarily give rise to many phenomena during its excretion; it causes salivation and symptoms of stomatitis in the mouth and gums. On the contrary, chloride of mercury is a substance which does not affect the mouth, and which does not induce the phenomena during its excretion observed with metallic mercury. a

We may regard it as a good rule, that it is preferable, at all times, to introduce into the system compounds which differ the least from the elements of the living tissue. As homogeneous drugs are accepted with the least expenditure of the vital forces, they are particularly adapted to the adynamic type of diseases; where the heterogeneous may not be counter indicated in the hy-peradynamic form of affections.