64 Some Recent Advances in Science — 



detecting the tubercle bacillus should now a few years later 

 furnish us with means, in certain cases at all events, of accom- 

 plishing its destruction. 



At the late National Congress at Berlin in August last Dr. 

 Koch read a paper in which he gave some of his experience in 

 the use of various germicides. He stated that he was then 

 carrying out investigations which he was sanguine would enable 

 him shortly to make known a remedy, which he believed ex- 

 erted a curative eifect on tissues infected by the bacillus tuber- 

 culosis. Some three months later he gave the account of the 

 action of this remedy, which created a world-wide excitement 

 unequalled in medical history. The composition of the remedy 

 was, however, kept a close secret. Those best acquainted with 

 Koch believed that his motives in doing so were perfectly dis- 

 interested, and that he only refrained from making its composi- 

 tion known until sufficient experiments had been made to prove 

 the importance of the remedy. The steps by which the discovery 

 was made have been already dwelt upon in Koch's own words 

 in the papers. At first, in conducting his experiments, he used 

 pure cultivations of the tubercle bacilli themselves, killed, 

 finely pounded, and suspended, and he found that, though these 

 injections had curative effects, yet they 'produced small sup- 

 purating centres. He sought, therefore, to find out how this 

 matter-forming tendency could be removed from the remedy, 

 and at last succeeded, by making a glycerine extract from pure 

 cultivations of the bacilli, in producing the remedy which is 

 now on its trial throughout the civilised world. The active 

 principle of the remedy is in consequence practically a derivative 

 of albuminous bodies, closely allied to the tox-albumens^ 

 though it is shown not to belong to them by its withstanding 

 high temperatures. The amount of this active principle present 

 Koch estimates at fractions of i per cent. How does Koch's 

 remedy act ? Koch's explanation, which he does not profess to 

 be by any means the final one, is that the bacilli form a necrosis- 

 producing substance. If to the already formed necrosis-producing 

 substance a still further artificially prepared one is added, not 



