148 THE LTSmS. 



hemolytic and spermotoxie action of the immune serum was due to 

 one and the same substance. 



Both Metschnikoff and Metalnikoff have obtained spermotoxie 

 sera which are active both in vitro and in vivo, and they have also 

 prepared anti-spermotoxins. In Metschnikoff's experiments the 

 spermotoxie serum of a guinea-pig was injected into a rabbit and 

 from the latter there was obtained an anti-spermotoxic serum. AlteF 

 three injections, the serum of this rabbit neutralized the spermotoxie 

 serum of the guinea-pig in the proportion of eight to one. Metal- 

 nikoff proceeded in an inverse way. He injected the spermotoxie 

 serum of a rabbit into guinea-pigs, both subcutaneously and intra- 

 peritoneally. After three injections, he obtained a feeble anti-spermo- 

 toxic serum, from twenty to twenty-five volumes of which neutralized 

 one volume of spermotoxie serum. He continued to give injections of 

 the spernrotoxic serum with the hope of obtaining a more active 

 anti-spermotoxin, but instead of reenforcing his product he found 

 that finally he obtained a serum which had absolutely no antitoxic 

 property. He could explain this only on the supposition that while 

 his spermotoxie serum contained two toxic fectors, the sensitizer and 

 the alexin, his anti-spermotoxic serum contained an anti-body for 

 only one of these factors. For the neutralization of the sensitizer 

 there must be produced an anti-sensitizer, while for the neutraliza- 

 tion of the alexin an anti-alexin is needed. On continuing his in- 

 vestigations along the line suggested by this theory he ascertained 

 that his anti-spermotoxic serum, which had been obtained from ani- 

 mals repeatedly treated with the spermotoxie serum and which had 

 shown no antitoxic action, became active on the addition of fresh 

 serum from a normal guinea-pig; for instance, one drop of the 

 spermotoxie serum plus ten dtops of the antitoxic serum heated to 

 56° plus three drops of the serum of a normal guinea-pig killed 

 spermatozoa within ten minutes ; while one drop of the spermotoxie 

 serum plus ten drops of the antitoxic serum heated to 66° plus three 

 drops of the serum of a normal guinea-pig heated to 56°, did not 

 kill spermatozoa. This shows that while the treatment of the ani- 

 mals with spermotoxie serum produced an anti-sensitizer, it did not 

 produce an anti-alexin. 



Metalnikoff has shown that auto-spermotoxins may be produced 

 in the animal body. If a guinea-pig be treated either intra,perito- 

 neally or subcutaneously with the spermatozoa of another guinea- 

 pig, the serum of the treated animal is toxic for the spermatozoa of 

 both. This auto-toxicity may be increased by repeating the injec- 

 tions and there may be obtained a serum ten drops of which added 

 to one drop of the spermatic fluid of either animal causes complete 

 immobilization of the spermatozoa within from three to four minutes. 

 This autotoxin conforms to the general laws of the cytotoxins. It 

 loses its toxic property on being heated to 55° and is easily regen- 



