ARTIFICIAL PRODUCTION OF TUBERCLE. 21 



little doubt remaining as to their perfect histological identity. They are in 

 both cases perivascular, and also extravascular, and they both equally pass 

 gradually into cheesy decay. 



I must confess that, sceptical as every one must naturally at first feel 

 on this subject, the cumulative force of the evidence in favour of the 

 tubercular nature of these growths appears to me to be irresistible. We 

 are either dealing with tubercle, or we have before us a new and hitherto 

 uaknown constitutional disease of the rodentia, consisting of growths which, 

 in their naked-eye appearances and histological characters, correspond with 

 all the essential features of tubercle in man; which occur not only 

 in the organs which are the chosen seats of tubercle in man, but also 

 in the same parts of those organs ; which have the same vital characters, 

 and the same early degenerative cheesy changes — not suppuration nor 

 acute softening — and with no marked characters sufficient to distinguish 

 them from tubercle. It would appear to me that, according to all our 

 ordinarily received rules of pathological definition and classification, this 

 disease must be considered tubercular; for the analogy is not one of mere 

 histological refinements, but also of seat of selection, mode of growth, and 

 vital characters : and, therefore, extraordinary as its mode of production 

 may appear, we are not on that account justified in excluding it from 

 the pathological category to which it appears properly to belong. The only 

 known disease which possesses the least affinity with it is leucocythsemia ; 

 but leucocythsemic growths are softer, whiter, and more milky or medullary 

 in appearance than these granulations, and they have not the same tendency 

 to degenerative changes, and they are, as an almost invariable rule, attended 

 with an increase of the white corpuscles of the blood, which these growths 

 are not. Tubercle also is similarly unattended, though such an increase might 

 be expected from the implication of the lymphatic apparatus.' 



I do not think that the disease can be considered as by any means 

 identical with farcy, though the local changes may bear some resemblance 

 to farcy changes ; but every subsequent change of farcy is one of a suppurative 

 kind in internal organs. 



After the recent specimens which I have submitted to you, I do not 

 think that any one can maintain that these changes can be included under 

 anything ordinarily understood by the term pyaemia. 



The great difficulty in the present day in identifying any disease with 

 tubercle depends, I think, on defective, and, as it seems to me, somewhat 



' Billroth, Beitrage, p. 147. 



