18 ARTIFICIAL PRODUCTION OF TUBERCLE. 



I examined could I find any granulations in the choroid, and the meningeal 

 arteries in aU cases examined appeared to be free from anything like tuber- 

 cular growths. 



To contrast these results with twelve cases of inoculation in rabbits, I 

 inoculated five with pus without producing any general affection ; but in 

 nearly all these there was extensive local suppuration under the skin, pro- 

 ducing in many cases large abscesses, which when old were filled with diffluent 

 curdy matter, but were not associated with the granulations described in the 

 guinea-pig. Microscopic examination of these showed that they consisted 

 of pus alone, and they presented none of the appearances described as charac- 

 terising the subcutaneous granulations. 



Inoculations with tubercle also on the rabbits, seven in number, only 

 produced distinct effects in two : and these were mixed with pneumonia and 

 with other internal inflammations, which had some appearance of being of 

 pyaemic origin, and in three cases with a laryngo-tracheitis extending to the 

 lungs, and having a strong resemblance to diphtheria in the adult (PI. I. 

 figs. 8, 9, 10). I mention these to show that the tubercular affection in the 

 guinea-pig is much more easily produced than in the rabbit. 



The most important question, however, in relation to these experiments is 

 that of the correspondence of these growths with what is ordinarily considered 

 as tubercle ; and, in discussing this, I will take as the type of tubercle that 

 pathological product concerning the nature of which there is the least 

 difference of opinion — viz., the grey granulation. There are, however, two 

 or three leading points which I should wish to lay before you with some 

 emphasis. One of these includes the mode of distribution, the multiplicity 

 of the affection, the organs affected, and the individual parts of the organs 

 so affected, which strikingly correspond to the chosen seats of tuberculous 

 affection in man. There is one exception in the guinea-pig — -viz., the absence 

 of meningeal affection ; but I do not think that this can weigh very materially 

 against the cumulative force of the argument derived from the other viscera, 

 especially as tubercular changes in the meninges do not form a necessary 

 accompaniment even of the process of general and acute tuberculosis in man. 

 It is possible also that the non-implication of the meningeal arteries in the 

 guinea-pig may depend on minute points in their anatomy with which we 

 are not yet familiar. 



I would also call your attention to the fact that, in all these organs, the 

 main characteristic of the affection is the production of a series of growths 

 resembling the lymphatic tissues, and probably having their starting-point in 

 structures of this nature. Now I think that, if there is one definition of 



