2G ARTIFICIAL PRODUCTION OF TUBERCLE. 



formation ; but even this scarcely appears to afford an absolute proof that the 

 infection is communicated by solid particles, though the presumption would 

 appear to be in favour of this hypothesis, since the absorption of colouring 

 matter by new growths is only what is observed under many different 

 circumstances in the animal economy. 



I may, perhaps, be permitted to say, as will perhaps appear from the 

 remarks that I have already made, that the morbid processes I have now been 

 describing appear to me to be absolutely removed from the ordinary phenomena 

 observed in the obstruction of vessels by emboli. I have already stated that 

 the obstruction of the vessels is a consequence, and not a cause, of the growth, 

 and the anatomical appearances observed differ widely from embolic phenomena. 

 "When a vessel is obstructed from within, there results a centre of anaemia 

 and of early necrobiosis of the parts supplied by it, surrounded by a zone 

 of injection ; while here there is an area of growth, generally proceeding from 

 certain limited centres, but surrounded by a zone, not of hyperaemia, but 

 of irregularly extending anaemia. 



In speaking, also, of septic absorption as a mode of production of 

 tubercle, I think that we must admit that these changes are to be placed 

 in a different category from the phenomena ordinarily classed under the term 

 of pyaemia. There is not a 'sign of suppuration to be observed in these cases 

 — at least, not in the internal organs ; and so infrequent are the appearances 

 of ordinary inflammation observed, that they may be almost said not to exist 

 — at any rate, as an essential part of the process. M. Lebert speaks of the 

 changes in the lung as a peri-bronchitis, or a peri-alveolitis, or a peri-arteritis ; 

 but all new growtli is not inflammation. The inflammatory nature of tubercle, 

 affirmed by Broussais and Cruveilhier, has been a ground of contention among 

 pathologists since the writings of the former appeared; but at any rate, if 

 the nature of the growth be inflammatory, it is an inflammation proceeding 

 under special conditions, and with peculiar limitations to individual tissues 

 and to special parts of individual organs. This latter condition, as well as 

 its mode of origin, are further arguments against the theories either of 

 embolism or pyaemia being applicable to this affection. Neitlier of these 

 commence with local granulations, or, as a rule, with the peculiar impli- 

 cation of the local lymphatics here observed. Moreover, the parts of the 

 organs affected further confirm this view. It would appear to be impossible 

 to regard the peritoneal granulations as the results of either of these pro- 

 cesses. Nor in the lungs, liver, spleen, or intestines, are either embolic or 

 pyaemic conditions so specially confined to the lymphatic structures, as they 

 are observed to be in these instances. 



