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26 Predisposition and Immunity. 



tozoa (spermolysins) , upon bacteria (bacteriolysins) , upon white 

 blood cells (leucolysins). Some dissolve several kinds of cells, as 

 in the case of spermolysins, which destroy red blood cells as well 

 as spermatozoa. From this it may be seen that in general 

 cytolysins possess specificity of action. 



The appearance of cytolysins in the body of any given animal 

 is occasioned by the introduction of cells of a different species of 

 animal into the first. If human blood be injected in increasing 

 amounts under the skin of a rabbit or into its peritoneum, the 

 serum of the rabbit will acquire the power of dissolving the hu- 

 man red blood cells, but not those of horses, cattle or guinea-pigs. 

 If the spermatic fluid of guinea-pigs be introduced into rabbits, 

 in the same way the serum of rabbits becomes solvent for the 

 spermatozoa of guinea-pigs, but cannot influence the spermatozoa 

 of another species of animal. If colon bacilli be injected into an 

 animal a cytolysin will be developed destructive only to these 

 microphytes, and in fact only to the particular strain of this 

 bacterial group which was employed in the experiment. 



From the foregoing it should be reahzed that the principal feature 

 in the production of immunity against foreign celhtlar elements is the 

 formation of the amboceptor or desmon, and that this alone is a new 

 product of the cells of the invaded body ; the other element, the alexine, 

 naturally pre-exists in every body, its combination with the desmon form- 

 ing the cytolysin. If, however, the necessary alexine be absent or present 

 in insufficient amount, the C3'tolysin will not appear. In this latter way must 

 be explained such occurrences as where, in spite of repeated introduction 

 into an animal of some type of cells, the blood acquires no cytolytic power, 

 but where on further addition of the serum (containing the required alex- 

 ine) from another species of animal cytolytic activity is immediately 

 produced. 



The sources of the amboceptors are apparently the bone- 

 marrow, spleen, lymph glands and perhaps the subcutaneous con- 

 nective tissues. 



In addition to the production of antitoxic and cytolytic sub- 

 stances the body may engage along the same line of reaction 

 in the formation of substances [II order of Ehrlich] which 

 cause foreign cells to aggregate in masses (clumping, agglutina- 

 tion), the so-called Agglutinins; and other substances which 

 coagulate foreign types of albumens (Coagulins) and cause their 

 precipitation (Precipitins). In illustration, if defibrinated human 

 blood be injected into a rabbit there is developed in the blood 

 of the latter a substance which will act on human blood to 



