234 ON SYMPATHY AND FASCINATION. 



To determine whether such a channel actually existed or not, Dr. Wollas- 

 ton introduced into the stomach three grains and a half of the salt called 

 prussiate of potash ; the presence of which, in almost all kinds of colourless 

 fluids, is capable of detection to the utmost nicety, by mixing with them a 

 small portion of solution of iron, the colourless compound being immediately 

 marked with a blue tinge. The above quantity was given to a healthy per 

 son, about thirty-four years of age, and was repeated every hour to the third 

 time. The natural secretion from the kidneys being tested every half hour 

 was found in two hours to be slightly dyed, and at the end of four hours to 

 afford a deep blue. At this period, just one hour after taking the last dose, and 

 when the blood-vessels might be supposed to be fully impregnated with the 

 material, if it passed to the kidneys through this conveyance, blood was taken 

 from the arm, and allowed to coagulate, so that the serum or limpid part of it 

 might be fully separated. The presence of the prussiate was then endea- 

 voured to be discovered, by means of the solution of iron, but without the 

 least effect, for the serum still remained colourless. And in other experiments 

 of a similar kind, made both by Dr. Wollaston and Dr. Marcet, it was satis- 

 factorily ascertained that the prussiate of potash, though it found its way 

 readily to the kidneys, did not exhibit any trace of its existence in the fluid 

 of any other organ whatever, any more than in that of the blood ; as the 

 saliva, the mucus of the nostrils, or the limpid discharge produced by blisters. 

 Mr. Home has since shown, that rhubarb introduced into the stomach in like 

 manner finds a path to the kidneys, apparently without passing through the 

 circulating system.* 



Mr. Home at one time suspected that the organ of the spleen afforded a 

 passage from the stomach to .the circulation of the blood in the cases before 

 us, instead of the lacteal vessels, which immediately rise from the alimentary 

 canal. This idea, he has, however, since relinquished as erroneous ; but had 

 even such a passage existed, it would not have answered the purpose ; for it 

 would only have conducted materials by another path to the blood; and the 

 experiments of Dr. Wollaston have sufficiently proved, that the unknown 

 channel, wherever it lies, has no connexion whatever with any part of the 

 system of biood-vessels, or even with the common system of absorbent ves- 

 sels : and so far he seems to have disproved a previous theory of Mr. Charles 

 Darwin upon this subject, which held, that the absorbent system might be- 

 come the channel, by assuming a retrograde action. Such action, however, 

 has never been established, and, independently of the experiments before us, 

 it is rendered highly inconceivable by the known structure of the absorbent 

 vessels themselves. 



The corollary, then, resulting from these observations, is, that in the animal 

 system, as well as in inorganic nature, bodies in various instances act where 

 they are not, and through channels of influence or communication, with which 

 we are altogether unacquainted. 



The examples thus far offered, in regard to animals, I readily admit, are 

 taken from different parts of the same individual frame: but as they are 

 drawn from parts remotely situated, and whose intercourse, so far as we are 

 able to trace it, is as much cut off as though they were of different frames, 

 excepting, indeed, by a channel which does not show itself to be resorted to 

 in the cases before us, I mean the blood ; they may serve to lay a ground- 

 work for our conceiving the possibility of a sfmilar influence or association 

 of action between different parts of different frames, or, which is the same 

 thing, between living body and living body. 



I proceed, then, to offer examples of this latter kind of influence. The sub- 

 ject, I am aware, is not only of a very curious, but of a very delicate nature, 



* The only mode by which the present writer can conjecture the possibility of these substances being 

 conveyed :o the kidneys by the course of the blood, and becoming manifest in their ordinary- secretion, on 

 the application of chemical tests, is, that they may be so minutely decomposed by the action of the blood 

 while passing through it, as to be beyond the influence of any tests whatever ; and that they only discover 

 themselves in the renal secretion, in consequence of a peculiar attraction or alitnity of the organ for such 

 materials, and their being hereby thown olf in a more concentrated foVm. But this explanation is. after 

 ail, merely conjectural. See Study of Med. vol. v. p. 283. 2d edition 



