360 BACTERIOLOGY. 



been confirmed again and again in the course 

 of manifold and varied experiments. It was 

 shown by Buchner that even blood that has 

 been frozen, and in which the wandering cells 

 have consequently been rendered wholly im- 

 potent, kills bacteria almost as quickly as fresh 

 blood-serum. On the other hand, blood that 

 is warmed to 6o-7o loses this power. From 

 these facts, we must infer that the blood- 

 pla'sma itself is able to kill bacteria in a 

 purely chemical way ; the substances in the 

 blood-plasma, which are thus effective are 

 the so-called " active proteids " or alexins. 

 But certain of these active chemical protect- 

 ive substances are also able to neutralize 

 the bacterial toxin, as we may conclude 

 from the fact that if active blood-plasma is 

 brought in contact with bacterial poisons 

 outside of the body, the poisonous action of the 

 latter is diminished or seems even to be com- 

 pletely annulled, whereas in the same blood in- 

 'side of the organism, chemical combinations 

 and oxidations or other transformations may 

 also play a part in rendering the poisons in- 

 nocuous or in eliminating them. The organ- 

 ism possesses in the peculiar chemical sub- 

 stance known as nucleic acid, which is found in 

 the cell nucleus, a substance that kills bacteria 

 and combines with basic poisons. A similar 



