BACTERICIDAL OR ANTI-BACTERIAL IMMUNITY. 185 



It has been found that the haemolytic capacity of the normal blood 

 serum, vhich in many animals, as we have seen, is very marked for the 

 corpuscles of alien blood, is also due to two substances which in charac- 

 ter and* action are similar to those which have been so carefully studied 

 in the lytic sera of artificially adapted animals. 



It is evident that this artificial haemolysis, secured by the adaptation 

 of one species of animal to the red blood cells of another, is quite analo- 

 gous to the process by which immunity is secured against pathogenic 

 bacteria cholera, for example and which is called bacteriolysis. Both 

 are specific examples of the general process called cytolysis, meaning cell 

 destruction. But this reaction of haemolysis is not only one of extraordi- 

 nary delicacy, but is easily observed under conditions quite within our 

 control, and permitting such elaborations and variations as involve great 

 technical difficulties when we are directly engaged with the phenomena 

 of bacteriolysis. 



Thus these studies of haemolysis have a practical significance in their 

 bearing upon our conceptions of bacteriolytic immunity quite apart from 

 the interesting general biological field into which they have led the way. 



The development of cytolytic capacities in the blood serum of the 

 living animal as the result of adaptation to bacteria and to alien red 

 blood cells being known, it was natural to extend the method to other 

 cells. Thus it has been found that in the adaptation of one animal to 

 the spermatozoa of another species by iutraperitoueal injections, a serum 

 is obtained which quickly brings to an end the movements of fresh sper- 

 matozoa of the species used spermolytic serum. 



Similarly, specific leucolytic sera have been procured by intraperito- 

 neal injections of emulsions of lymph nodes, spleen, and bone marrow. 

 Such lencolytic sera may not only destroy the leucocytes outside of the 

 body, but they are extremely toxic when introduced into the living spe- 

 cies from which the tissues originated. The effects of these leucolytic 

 leucotoxic sera in the body are most pronounced in the blood-form- 

 ing organs. Here, as the studies of Flexner ' show, a very significant 

 impulse to new cell formation may be associated with the action of the 

 leucotoxic sera. 



Emulsions of kidney cells of one species injected into the peritoneum 

 of another have led to the development of nephrolytic serum ; that is, se- 

 rum which on injection into the body of an animal of the same species as 

 that furnishing the kidney cells induces noteworthy degenerative changes 

 in the kidney. Thus, also, hepatolytic, 2 pa ncreolyiic, thyreolytic, neurolytic, 

 and other analogous cytolytic substances have been developed. 



So far as they have been studied, the nature of the active agents in 



1 Flexner, Bull. Univ. Penna, vol. xv., 1902, p. 287; also Bunting, ibid., vol. xvi., 

 1903, p. 200. 



-For a study of nephrotoxins, see Pearce, Bull. Univ. Penna., July and August, 

 1903 The studies of Pearce recorded in a paper read before the American Association 

 of Pathologists and Bacteriologists in April, 1904, and unpublished at the date of this 

 writing, indicate that in the adaptation of animals to many alien parenchyma cells the 

 new-formed substances are less specific than has been commonly assumed. 



