CYTOTOXINS 151 



them five or six injections of ten to twenty grammes 

 of dog brain and spinal cord mixed with normal 

 salt solution. The serum of these ducks injected 

 intracerebrally into dogs in doses of 0.5 c.c. 

 caused the dogs to die almost at once in complete 

 paralysis, whereas if normal duck serum was in- 

 jected in the same way no effects of any kind were 

 produced. If smaller doses of the specific neuro- 

 toxic serum were administered, say o.i to 0.2 c.c., 

 various paralyses and epileptiform convulsions set 

 in, from which the animals sometimes recovered. 

 The action of this serum is specific, i.e., the serum 

 of ducks treated with dog brain causes these symp- 

 toms only in dogs, while on rabbits it acts no 

 differently than normal duck serum. 



Spermatoxin. Another specific cell-dissolving 

 serum was produced by Landsteiner, Metchnikoff, 

 and Moxter, by injecting animals with the sperma- 

 tozoa of other animals. Such a serum rapidly 

 destroys the spermatozoa of the animals whose 

 product was injected. This cytotoxin was named 

 spermatoxin. If animals are treated with spermato- 

 zoa there is produced a serum which is not only a 

 spermatoxin, but which is also haemolytic for the 

 red cells of that animal. This was demonstrated 

 by Metchnikoff and Moxter, and has already been 

 referred to in discussing haemolysins. If, for ex- 

 ample, we inject the spermatozoa of sheep into 

 rabbits, we shall obtain a serum that is sperma- 



