TEXT-BOOK OF BACTERIOLOGY. 133 



power of serum depends on the salt which it contains: a diminution 

 of its saltness is accompanied with a diminution of its power to kill 

 bacteria. One might, for a moment, be tempted to suppose that 

 it is the mineral ingredients which, directly and immediately, serve 

 as the basis of disinfecting power in the serum. Yet Buchner 

 shows clearly that such cannot be the case, and that the salts are 

 only of importance because they stand in intimate relation to the 

 albuminoid matter of the blood, the quantitjr and quality of which 

 is decisive, and turns the scale one way or other. The salts serve 

 as solvents, or agglutinants, to the albuminates, and an altogether 

 special, peculiar, and as yet unexplained condition of the serum 

 albuminoids is the active cause of the bacteria-killing agency. 



Many celebrated investigators are of the opinion that dead albu- 

 min, such as we have hitherto almost exclusively employed in our 

 researches, is widely different from the living albumin of the body 

 in its chemical composition and also in its behavior. Thus it per- 

 haps possesses qualities hostile to bacterian life which have hitherto 

 escaped us, and it will be the task of future investigators to throw 

 more light on all these matters. 



There is no doubt that our knowledge of the means for re- 

 sisting bacteria which an organism possesses has been very con- 

 siderably increased by the observations whose results we have 

 just considered. In one point, however, they are not quite satis- 

 factory. Buchner and Nissen experimented almost exclusively 

 with the blood of dogs and rabbits; both apply the results obtained 

 in a general manner, and speak simply of " blood " and " blood- 

 serum," without distinguishing the animals whence it was obtained. 

 But the experiments of Petruschky, and still more those of Behring, 

 have shown that the different species of animals show marked dif- 

 ferences, and that the blood of the frog and the rat, for instance, 

 show qualities not to be met with in that of other animals. This 

 would lead to the supposition that the differing susceptibility of the 

 animals might be an important factor in this question, and might 

 deserve more attention than it has hitherto received. 



However that may be, what has been written can only strengthen 

 our belief that the processes by which the body resists the bacteria 

 are chiefly of a chemical nature. 



But it would be unfair to mention this view of the case and no 

 other. A large number of investigators whose opinion is worth 

 listening to, do not believe that the organism makes use of such 

 means to attain its object, but that the relation between the two 

 hostile elements expresses itself in an immediate struggle between 

 the cells of the body and their foreign invaders. 



