X. EFFECTS OF DEFICIENCY 463 



and ill the circulatory organ of the cat, in the absence of the eserine that 

 inhibits the enzyme choHnesterase. 



The liberation of thiamine (or a thiamine ileri\'ativ(0 by nerve action was 

 for the first time demonstrated by Minz.'" LwotT" had devised a highly 

 sensitive microbiological method for the estimation of very small Cjuantities 

 of thiamine, using Flagellatae. With this method Minz com])ared the libera- 

 tion of thiamine from excised resting ox nerves with that of electrically 

 stimulated ner\'es. He was able to pro^'e that the stimulated nerves deliv- 

 ered much more thiamine than the resting nerves (four to eight times as 

 much). Shortly afterward these results were confirmed and extended by 

 von ]\Iuralt. This Swiss investigator has given a review of all the work, 

 mostl}' from his own laboratory, on thiamine and peripheral neurophysi- 

 ology.'- ^^on Muralt and his collaborators quickly froze exited nerves or 

 resting nerves in liquid air. The frozen nerves were ground in a mortar and 

 extracted for only 10 minutes with Ringer's solution. The thiamine content 

 of the extracts was estimated by several different methods. The extracts of 

 the stimulated nerves were richer in thiamine than the extracts of the 

 resting nerves. This means that thiamine in the exited nerves is in such a 

 state that more can be extracted by Ringer's solution in 10 minutes than 

 can be obtained from a corresponding sample of unexcited nerves. The 

 different methods for estimating the liberated thiamine yielded on the whole 

 practically the same results; however, the yeast ferment method of Atkin, 

 Schultz, and Frey showed much lower values for the thiamine content of 

 both excited and resting nerves; and also the difference between excited 

 and unexcited nerves had disappeared. It was not yet possible to give an 

 explanation for this discrepancy. Furthermore it was difficult to draw con- 

 clusions from these experiments because A. Wyss and F. Wyss'* in the 

 laboratory of von Muralt found that by poisoning the nerves by mono- 

 iodoacetic acid more thiamine is obtained in the extract of resting nerves 

 than in the extract of excited nerves. In most experiments thiamine exerts 

 an inhibiting effect on the vagus or acethycholine action on the heart. By 

 replacing certain groups in the thiamine molecule by other groups, the 

 effect is mostly reduced but not abolished. It is amazing, however, that 

 the thiamine pyrophosphate has no action at all! 



From all these facts it may be assumed that thiamine or a thiamine 

 compound plays a role in neurophysiological activity. 



However, there is as yet no convincing evidence that the neurological 

 active substance is thiamine itself or one or more derivative(s) of thiamine. 



•» B. Miiiz, Compt. rend. soc. hiol. 127, 1251 (1938). 

 >' M. Lwoff, Compt. rend. soc. bid. 128, 241 (1938). 

 '= .V. von Muralt, Vitamins and Hormones 5, 93 (1947). 

 " A. Wyss .ind F. Wyss, Experientia 1, 160 (1945). 



