CHAPTER XIV. 



SOME SPECIAL PROPERTIES OF BLOOD SERUM. BACTERI- 

 CIDAL ACTION. PRECIPITINS, AGGLUTININS, 

 BACTERIOLYSINS, HEMOLYSINS. 



SELF PRESERVATION OF THE BLOOD. 



In earlier experiments on transfusion of blood to supply a 

 loss brought about by excessive bleeding it was recognized 

 that the added blood sometimes seemed to act as a poison to 

 the individual to whom it was given. It was found later that 

 this toxic action followed the passage of blood from one species 

 of animal to another, but that the transfusion from man to 

 man, from dog to dog or from rabbit to rabbit was not accom- 

 panied by the same danger. Such observations were fre- 

 quently made and gradually led to the conclusion that the 

 plasma or serum of the blood of each animal contains a some- 

 thing which has a destructive action on the corpuscles of other 

 bloods and which may be designed to protect the blood from 

 the action of any foreign substance. Various theories have 

 been put forward to explain this recognized property of the 

 serum. As yet our knowledge in this field is largely of the 

 empirical order, and scarcely suitable for clear elementary 

 presentation. But the importance of the subject as thus far 

 developed is so great that a short chapter on what seems most 

 satisfactorily established may not be out of place. The phe- 

 nomena in question are certainly chemical and from this side 

 must receive their final explanation. Numerous related phe- 

 nomena are found to call for the same kind of consideration. 



It has long been known that the large white cells of the 

 blood, the so-called leucocytes, have the peculiar power of 

 destroying bacteria or other foreign cells which find their way 

 into the blood stream. Hence these corpuscles have been 

 called phagocytes or devouring cells. This destruction of 



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