214 GERMICIDAL SERA 



is still germicidal. 5. Blood in which coagulation is prevented by 

 the addition of 25 per cent, of magnesium sulphate, has its germicidal 

 properties decreased. 6. Filtered blood plasma from the horse is 

 germicidal. 



At one time, Behring attributed the action of the blood of the 

 white rat on anthrax bacilli to its alkalinity. He made titrations which 

 showed that the blood serum of the rat is more alkaline than that of 

 certain susceptible animals, as the cow, rabbit and guinea-pig. How- 

 ever, there are other and more important points in which these animals 

 differ from the rat than in slightly less blood alkalinity. Had he shown 

 that the blood of the adult rat, which is highly resistant to anthrax, is 

 more alkaline than that of the young rat, which is more susceptible, 

 his argument would have been more reasonable; but even then it 

 would not be convincing evidence. 



In 1890, Buchner made valuable contributions to our knowledge 

 of the germicidal properties of blood and stated his conclusions as fol- 

 lows : 1. The germicidal action of blood serum is not due to phagocytes, 

 because it is not influenced by the alternate freezing and thawing of 

 the blood, by which the leukocytes are destroyed. 2. The germicidal 

 properties of the cell-free serum must be due to its soluble constituents. 

 3. Neither neutralization of the serum, nor the addition of pepsin, nor 

 the removal of carbon dioxid gas, nor treatment with oxygen, has any 

 effect on the germicidal properties of the blood. 4. Dialysis of the 

 serum against water destroys its activity, while dialysis against 0.75 

 per cent, salt solution does not. In the diffusate there is no germicidal 

 substance. The loss by dialysis with water must be due to the with- 

 drawal of the inorganic salts of the serum. 5. The same is shown to be 

 the case when the serum is diluted with water and when it is diluted 

 with salt solution ; in the former instance the germicidal action is 

 destroyed while in the latter it is not. 6. The inorganic salts have in 

 and of themselves no germicidal action. They are active only in so 

 far as they affect the normal properties of the albuminates of the 

 serum. The germicidal properties of the serum reside in its albumin 

 constituents. 7. The difference in the effects of active serum and 

 that which has been heated to 55 C. is due to the altered condition of 

 the albuminate. The difference may possibly be a chemical one (due 

 to changes within the molecule) or it may be due to alterations in 



