in GREEN AND BROWN FROG 133 



experimented that the muscles became rigid at the 

 place where caffein was injected, and this rigidity 

 gradually extended to the rest of the body, but he 

 failed to observe any tetanus. About three years 

 afterwards, Aubert arrived at results entirely opposed 

 to those of Johannsen, rinding that caffein in the 

 frogs with which he experimented produced marked 

 tetanus, but very slight rigor. These contradictory 

 results induced Schmiedeberg again to take up the 

 subject, and he found that the discrepancy be- 

 tween the statements of Johannsen and Aubert was, 

 to a great extent, due to the kind of frog employed 

 by each observer in his experiments, the former having 

 used specimens of R. temporaria, and Aubert of 

 R. esculenta. According to Schmiedeberg, in R. tern- 

 poraria caffein produces muscular rigor, without 

 tetanus, the rigor beginning at the place where the 

 poison is applied, and extending over the body so 

 gradually that the muscles first attacked may be 

 completely contracted and rigid, while others may be 

 still slightly irritable. On the other hand, in R. 

 esculenta, caffein frequently produces a violent and 

 continuous reflex tetanus, without any rigidity of 

 muscle other than that dependent on the tetanic con- 

 traction. It is only at a late stage of the poisoning, 

 two or three days after the caffein has been given, that 

 these differences between these two kinds of frogs 



