20

ELEMENTS OF MATERIA MEDIC'A.

necessary to the action of the poison; for if the circulation of a part beobstructed, the poison will no longer act. These reasons are, to my mind,conclusive, that in a large number of instances at least, if not in all, theoperation of a medicine on remote parts of the system depends on itsabsorption. Nor can I admit that this opinion is at all invalidated bythe arguments and experiments of Messrs. Morgan and Addison.

The principal objections which have been raised to the theory of theoperation of medicines by absorption, are the following:—

a. The experiments of Magendie and others, it has been observed,only show that a poison may get into the veins, and do not prove thatabsorption is essential to the effect. “ We must strongly protest,” sayMessrs. Morgan and Addison, “ against the assumption that, because apoison has been found to enter and pass through a vein, it is thence to beinferred that such a process is, under all circumstances, absolutely neces-sary to its operation.” But it has been proved that the more absorptionis facilitated the more energetic do poisons act, and vice versa.

b. Mr. Travers, in his Further Inquiry concerning Constitutional Irri-tation, points out very forcibly the analogy to be observed between theeffects of severe injuries and of poisons which operate rapidly on thesystem. Thus both strychnia and punctured wounds cause tetanus, andhe, therefore, concludes their modus operandi must be identical: con-sequently, as there is nothing to absorb in the one case, so absorptioncannot be essential in the other. But although the symptoms causedby the above poison are very analogous to those of traumatic tetanus,yet we are not to conclude that the effects of strychnia and of a punctureare precisely alike. “ The lact of two substances producing similarsymptoms in one organ,” observes Miiller {op. cit. p. off) “ does not provethat these substances produce exactly the same effects, but merely thatthey act on the same organ, while the essential actions of the two maybe very different.” And I confess I see nothing unphilosophical insupposing that the same morbid condition of a part may be induced inmore than one way: tor as every part of the organism depends for theperformance of its proper functions on the receipt of arterial blood and ofnervous influence, so alterations in the supply of either of these essentialsmay modify or even suspend the functions of a part.

c. Messrs. Morgan and Addison tell us that the blood circulating inthe carotid artery of a dog poisoned by strychnia is not poisonous to asecond dog, and they therefore infer that this poison does not act on thebrain by absorption, but by an impression upon the sentient extremitiesof the nerves.

By the aid of a double brass tube, (fig. 9,) consisting of two short brasscylindrical tubes to each of which a long handle is attached (fig. 11), theyestablished a complete circulation between the carotids of a poisonedand of a sound dog, by connecting the lower and upper ends of the dividedarteries in both animals, so that each supplied the brain of the otherwith the portion of blood which had previously passed through thecarotid artery to his own, and, consequently, the poisoned dog in thiscase received from the unpoisoned animal a supply of arterial blood equalto that with which he was parting. (Fig. 10.) One of the dogs was theninoculated with a concentrated preparation of strychnia, which had beenfound upon other occasions to produce death in these animals in aboutthree minutes and a half. In three minutes and a half the inoculated