TISSUE REACTION. II 



9. As is now well known, cell proliferation may be set up by 

 very numerous and very various forms of irritants, but the results, 

 though varying greatly in degree, are absolutely one in kind. Apply 

 any irritant to a surface or a tissue, and the result is a proliferation of 

 the cells. This appears to be the case especially in the connective 

 tissue group, where the increase in the number of cells is extremely 

 marked. Further, with this increased cell formation there is appa- 

 rently a taking up of the irritant material by the cells, and if one 

 cell is not sufficient for the task, a number combine to form plas- 

 modia (practically giant cells). That the taking up of these particles 

 or products further lowers the vitality of the cell, is evidenced by 

 the fact that as soon as the cell becomes filled with particles, it 

 dies, 1 and with its contained material acts as an irritant to other cells. 

 The chemical products, then, may be looked upon as the prime 

 movers in bringing about a proliferation of the cells with which they 

 come in contact, by which proliferation the cells appear to attempt to 

 get rid of the irritant material, and their resisting power is thus 

 greatly weakened. At this point the direct action of the bacillus 

 on the cell comes into play. The bacillus attacks the weakened 

 cell, and applies to its own use the rich store of proteids contained 

 within the highly organised but comparatively non-resistant cell. 

 By the aid of this store of proteids it acquires sufficient energy to 

 reproduce its like by asexual spores, the tissue cells are gradually 

 reduced to the peculiar caseous nodules so characteristic of tubercle 

 masses, the degree of caseation in many cases corresponding appa- 

 rently to the number of the bacilli. The physiological products are 

 sent into the surrounding tissues, and the process is repeated. From 

 this caseous centre the bacilli with their products may be carried to 

 mucous surfaces, and thence to the lymphatics, and even veins ; or 

 they may make their way directly to the lymphatics, where in some 



some of them certainly exert analytical functions before their synthetical functions 

 come into play. And it can scarcely be held for a moment that the Darwins have 

 proved that insectivorous plants are animal because they flourish so much more 

 luxuriantly when they have presented to them complex proteid substances on 

 which they also certainly exercise their analytical functions before their synthetical 

 functions are called forth. 



1 Metschnikoff, " History of Inflammatory Process : " Quart. Journ. Micros. 

 Set., January 1884. 



