understood conditions of disease. It is an equally necessary result that under the continued influence of opium the constantly constringed vessels should assume a new local function; that nutrition should be arrested in the parts which those vessels supply with blood; and that the shrunken, impoverished body of the confirmed opium-eater should be an outward and visible sign of the internal changes which are being so assiduously and determinately carried into effect by the narcotic.
When these facts respecting the direct physical action of various toxical agents on the body, through the line of the involuntary nervous system, are understood, they connect, through the same direction, the effects of more refined and much less definable influences. They show how psychological phases are ever at hand to modify nutritive changes: how grief, which shocks and dissevers the organic nervous supply, affects the animal life so deleteriously, exciting and reducing, and sometimes in part disabling altogether parts of the organic nervous track. They indicate how an equable nervous current is conducive to permanent nutritive activity and health, and show physiologically that to laugh and grow fat is after all a mechanical proposition. I must not, however, be tempted away into an inviting field of observation, in which the physical and the metaphysical so neatly blend.
It is worthy of remark that the action of the different toxicants to which I am directing attention, and which are in most common use among members of the human family, have in some cases a similar action, and in other cases a dissimilar action on the members of the lower creation. The alcohols appear to possess a toxical influence throughout all the domain of living animal beings. I can find no animals that escape the immediate action of the alcohols, or the remote effects which occur when the changes excited by the alcohols are often repeated. All our domestic animals come quickly under the ban. Birds and fishes do the same. Chloroform, chloral hydrate, and absinthe seem to exert a similar wide range of action. Tobacco is not so extended in its range. There are animals that can take with perfect impunity a dose of tobacco which would poison three or four men. The goat is an animal which can resist the noxious, but to it innoxious, weed.
Opium can be resisted by certain animals with equal readiness. A pigeon will practically live on opium. A pigeon will swallow with impunity as much solid opium as would throw twelve adult men into the deepest narcotism. Indeed, it is not correct to say that to pigeons opium is in any sense a poison.
The reasons for these exceptions are not clearly made out. The probability is, that the animals which take the intoxicants with so much impunity produce some form of decomposition of the agent in their own bodies, by which the active alkaloidal substance is rendered neutral in effect, or, at all events, is much neutralized.
