88 BACTERIOLOGY. 



agulating casein and of dissolving proteid. 

 Kocli has made use of the ability of many 

 bacteria to peptonize, dissolve and liquefy 

 gelatin as a basis for the separation of bacteria 

 into groups. 



Yet more remarkable is the fact that active 

 blood-serum and active tissue juices, fresh milk, 

 etc., possess the ability to kill bacteria and 

 sometimes display extraordinary activity in this 

 direction. H. Buchner was the first to recog- 

 nize and demonstrate this ; he was able by 

 heating these substances to 6o-7o to annul 

 their effect. Behring next recognized that 

 active blood-serum can nullify the effect of bac- 

 terial poisons. The addition of carbolic acid, 

 thymol, cresol, toluene, or chloroform, partially 

 preserves the activity of these 'body-fluids as 

 it does that of enzymes. Certain of these 

 active proteid bodies act precisely like enzymes, 

 so that between the newly discovered group 

 and the old no sharp line of demarcation can be 

 drawn. When carefully dried, both groups of 

 substances withstand high temperatures, while, 

 in a moist condition, their power is destroyed 

 by heating. Many of the " specific " bacterial 

 poisons belong to this group of enzymes and 

 active proteid bodies. 



Behring was the first to recognize that one 

 substance ordinarily alleged to be an effective 



