236 BACTERIA. 



" This purification of the glycerine extract has, however, no advantages as 

 regards practical application, as the substances removed have no action on 

 the human organism, so that the purifying process would only involve un- 

 necessary expense. The constitution of the active principle can, as yet, be 

 only a matter of conjecture. 



" It appears to me, indeed, to be a derivative of albuminous 

 bodies, and to be closely related to them, but it does not 

 belong to the group of so-called toxalbumens, as is proved 

 by the fact that it can withstand high temperature, and in 

 the dialyzer it passes quickly and easily through the mem- 

 brane. The quantity of active principle present in the 

 extract is in all probability very small. I estimate it at a 

 fraction of I per cent. Thus, if my assumption be correct, 

 we have to deal with a substance, the action of which on the 

 tuberculous organism, far surpasses that of the strongest 

 drugs known. 



" Various hypotheses may of course be formed as to the 

 specific mode of action of the remedy on tuberculous tissue. 

 Without in any way affirming that mine is the best possible 

 explanation, I imagine the process to be as follows : The 

 tubercle bacilli in their growth produce in the living tissues 

 just as in the artificial cultivations certain substances which 

 exert various but always deleterious influences on the living 

 elements surrounding them, the cells. Amongst these 

 substances is one which, in a certain concentration, destroys 

 living protoplasm, and causes it to undergo a transformation 

 into the condition called by Weigert, ' coagulation-necrosis.' 

 The tissue having thus become necrotic, the conditions are 

 so unfavourable to the nutrition of the bacillus that it is 

 unable to undergo further development, and finally, in some 

 cases, it dies off. In this way I explain the remarkable 

 phenomenon, that in organs freshly attacked by tuberculous 

 disease for instance, in a guinea-pig's spleen or liver filled 

 with grey nodules numerous bacilli are found, whilst bacilli 

 are rare or entirely absent when the enormously enlarged 

 spleen is made up of whitish substance in a condition of 

 coagulation-necrosis, such as is often met with in guinea- 

 pigs that die of tuberculosis. A solitary bacillus, however, 

 cannot produce necrosis at any great distance from itself, for, 

 as soon as the necrosis has covered a certain area, the growth 

 of the bacillus and, in consequence, the production of the 

 necrosis-producing substance diminishes, and thus a sort 



