222 M. F. GUYER 



resection or occlusion of the ductus deferens may similarly be 

 due to the action of a spermatotoxin. For spermatozoa which 

 could not leave the testis must ultimately die and be resorbed, and 

 it seems probable that upon their resorption spermatotoxins 

 would be formed which could attack the living germ-cells of the 

 testis. Depending upon the virulence of such toxin, complete 

 or partial sterility might ensue. However, that occlusion of 

 the efferent duct of one testis does not always prevent the forma- 

 tion of spermatozoa by the other testis — at least permanently^ — is 

 evident from the many cases known in man where an orchitis 

 or an epididymitis of one testicle has resulted in such occlusion 

 on one side, and yet the individual has remained fertile. 



SUMMARY 



1. Spermatotoxic sera, prepared by injecting fowls repeatedly 

 with the spermatozoa of rabbits, are toxic in vitro for the sperma- 

 tozoa of both rabbits and guinea-pigs. 



2. When introduced into the blood stream of male rabbits 

 at intervals for four or five weeks, such serum i^roduced partial 

 or complete sterility. Inactivation of many spermatozoa, reduc- 

 tion in numbers, or even complete disappearance from • the 

 semen occurred. In one case the sterility was partial or tempo- 

 rary; in a second, complete, when judged by the breeding test, 

 although the germinal epithelium appeared to remain normal 

 and a few spermatozoa were visible; in a third, complete, accom- 

 panied by marked degenerative changes in the testicles. 



3. Microscopical examination of the testes of the latter indi- 

 vidual (rabbit 83) showed that not only were the mature spermato- 

 zoa affected, but disintegrative changes had taken place or were 

 in progress in the seminiferous tubules. 



4. The blood-serum of a rabbit injected intravenously with 

 its own spermatozoa becomes highly toxic for the spermatozoa of 

 rabbits, including its own. 



5. The spermatozoa of a rabbit which has been repeatedly 

 injected with its own semen are much less viable, both in normal 

 rabbit serum and in spermatotoxic serum, than are normal 

 spermatozoa. Presumably such spermatozoa have been in- 



