THE LTSINS. 146 



from time to time and submitting them to examination^, he ascer- 

 tained that while the homologous cells were not altered and still 

 retained their motility, the heterologous cells soon lost their 

 motility. 



Metschnikoff* injected the spermatic fluid of one guinea-pig 

 into the peritoneal cavity of another, and found that after some 

 hours the spennatozoids were taken up by the leucocytes. After 

 this,, he injected into the peritoneal cavities of guinea-pigs sperma- 

 tozoa of several species of animals, and obserrod that many of these, 

 while still alive, are taken up by the leucocytes. The head of the 

 spermatozoon is first absorbed by the leucocyte, and for some time 

 thereafter the tail continues motile. Finally, however, the tail, as 

 well as the head, is taken into the leucocyte, and is apparently di- 

 gested. Twenty-four hours after the injection, heads of spermatozoa 

 within the leucocytes become more rare, and finally none can be seen. 

 The majority of the spermatozoa are taken up and digested by the 

 mononuclear leucocytes. Metschnikoff was not able to observe any 

 digestion of spermatozoa outside of the leucocyteSj and it may be 

 stated here that no one has as yet prepared a fluid which dissolves 

 spermatozoa. As we shall see later, sera have been obtained which 

 destroy the motility of spermatozoa, but the specific substances con- 

 tained! ia these sera are spermotoxins rather than spermotolysins. 

 Im pursuing his investigations Metschnikoff found that after all of 

 the injected spermatozoa had been absorbed from the peritoneal 

 cavity of the guiiiear-pig, that animal furnished a serum which im- 

 mobilized the spermatozoa of the animal furnishing the material with 

 which it had been treated. Later, by the subeuta/neous treatment of 

 rabbits with spermotoxic serum obteined from guinea-pigs, he pro- 

 duced anti-sl»rmotoxic substances and found that spermatozoa re- 

 tained their motility when placed in mixtures of spermotoxic and 

 anti-spermotoxic sera. Thisi anti-body may be developed in castrated 

 as well as in normal animals, showing that other eella of the body may 

 produce the substance. Moxter ^ injected the spermatozoa of the ram^ 

 suspended m physiological salt solution, into the peritoneal cavities 

 of guinea»-pigs. After twenty-five mimutes, the spermatozoa, in part 

 still motile, were seized upon by the leucocytes, and after twenty- 

 four hours no free spermatozoa could be founiL There was observed 

 at no time any evidence of dissolution of the' spermatic cells. This 

 phenomenon, it will be seen, is quite contraary to that observed on the 

 introduction of erythrocytes into the peritoneal cavity of an animal 

 of another species. The serum of the treated guinea-pig was found 

 to possess marked spermatocidal properties. Whea the living sper- 

 matozoa of the ram were divided into two portions, one of which was 

 treated with the serum of a normal guinea-pig and the other with 



' Awiwlea de V InaliMit Pasteur, 1899. 

 ' Deutsche med: Wochensckrifi, 1900. 



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