8o THE SIMPLER NATURAL BASES 



methylguanidirie is greatly increased (up to I -9 gr. of the gold salt 

 per litre; Koch [1912]) and fairly large quantities are also present in 

 the urine of animals killed by anaphylactic shock or by burning 

 (Heyde [1911, 1912]); normal urine only contains traces. The 

 symptoms of anaphylactic shock cannot, however, be reproduced in 

 any way by the administration of the base [Loewit, 1913]. 



Methylguanidine is distinctly poisonous ; 0*2 grm. administered 

 hypodermically killed a guinea-pig (Brieger [1886, I, p. 38]). The 

 smallest dose producing a distinct effect in a frog (fibrillar twitchings 

 of dorsal muscles) is I mg. ; 50 mg. is fatal. The base acts peripherally 

 on the nerve endings in the muscle ; large doses produce tetanic con- 

 vulsions (Gergens and Baumann). The action is similar to that of 

 guanidine, q.v. 



Methylguanidine in the organism is probably derived from creatine 

 and the amount in the urine is increased after feeding with meat ex- 

 tracts (Achelis [1906]). The mechanism of this change is not clear, 

 for the simple decarboxylation of creatine would yield dimethylguani- 

 dine, so that in addition to carbon dioxide a methyl group must be 

 removed by oxidation. There is however some indirect evidence that 

 bacteria can bring about the conversion of creatine into methylguani- 

 dine(Bocklisch[i887]). 



E. as-Dimethylguanidine, NH : C/ 



\NH 2 



This base appears to accompany the monomethyl derivative in 

 normal urine; Engeland isolated 0*15 grm. of the aurichloride from 2 

 litres of dog's urine, and the picrolonate was probably obtained from 

 human urine by Kutscher and Lohmann [1906, 3, 4]. 



The formation of as-dimethylguanidine by bacterial decarboxylation 

 of creatine has not yet been observed (cf. Twort and Mellanby 

 [1912, under creatine]). 



