ARTIFICIAL PRODUCTION OF TUBERCLE. 29 



of the changes found in the inoculated animals. The failure also of nearly 

 half of the experiments with inoculation, most of which animals were killed, 

 and in which no trace of tuhercle was fovmd — viz., fifty-three animals out of 

 one hundred and seventeen — proves strongly that tuhercle is not naturally a 

 common disease among them. 



In what the predisposition may consist, must remain to some extent an 

 open question. I admit that I am strongly inclined to regard it as depending 

 on some peculiar anatomical or physiological condition of the lymphatic 

 system, which renders it specially prone to react under septic agencies. 

 Both the lung and also the omentum of the guinea-pig are largely endowed 

 with lymphatic structures — more so, I think, than are to he found in these 

 organs in man ; hut positive proof of this kind is very difficult of attaioment. 



The fact of special aptitude for the action of poisons in particular indi- 

 viduals remains, however, a very positive one. It is shown by the escape of 

 some of the inoculated animals when the same material was used on more than 

 one ; and the effect of this predisposition in some cases of other poisons which 

 affect the lymphatic tissues, is well illustrated in the case of typhoid fever — a 

 disease which especially attacks the young, while those past middle life have a 

 greater comparative immunity. The explanation of this has long been taught 

 at University College, by Sir "William Jenner, to depend on the progressively 

 diminishing nutritive activity of the follicular apparatus of the intestines and 

 spleen with advancing life, rendering these structures less liable to be influ- 

 enced by this specific poison. 



The relative susceptibility of different genera of animals to this class of 

 agencies has not yet been the subject of any extended experiments. Those 

 hitherto made have been principally conducted with tuberculous matters, but 

 without any very positive results. In one case only is general tuberculosis in 

 a dog recorded by M. Rostan as a result of this proceeding. In other cases, as 

 in a lamb and a ram by M. Colin, tubercles were found only in the lungs ; and 

 the same result was twice observed by M. Villemin in cats. M. Lebert also 

 once observed granulations in the lungs of a dog which was the subject of a 

 biliary fistula, and in which he injected phosphoretted oil into the rectum. 

 But local growths in the lungs alone, though possibly tuberculous in their 

 nature, do not, as I have before stated, afford the conclusive proof which I 

 think that we at present require, and which is yielded by the multiplicity of 

 the affection in many organs. In other animals, as in a goat, a cock, and a 

 wood- pigeon (Villemin), or in a crow, cat, and fowl (Vogel), the experiments 

 hitherto conducted have been without results". It would appear desirable that 

 these should be conducted on a yet more extended basis. 



