408 ANNALS NEW YORK ACADEMY OF SCIENCES 



cm. length, the total electric energy released per gram and impulse was 

 found to be 47 micro-calories, on the average. There are some as- 

 sumptions, on which these figures are based, which will be discussed by 

 Drs. Cox, Coates, and Brown. If we consider all probable assump- 

 tions, these figures may possibly be revised downward by 15 per cent 

 or upward up to 100 per cent. 



Tested under the same conditions, the energy released by the break- 

 down of phosphocreatine was found to be 32 micro-calories per gram 

 and impulse, in the large eels (average of 15 experiments). In the 

 medium-sized eels, the energy released by phosphocreatine was about 

 51 micro-calories (average of 15 experiments). The lactic acid forma- 

 tion released about 17 /xcal., in the large, and 53 /xcal. in the medium- 

 sized, eels per gram and impulse. The energy of the lactic acid is prob- 

 ably used to rephosphorylate creatine, just as in muscle where the 

 phosphopyruvic acid transfers its phosphate via adenosine triphosphate 

 to creatine ("Parnas reaction"). The sum of the two reactions may, 

 therefore, be used as indication for the energy released by phosphate 

 bonds. It amounts to 49 /xcal. in the large, and 104 ;u,cal. in the 

 medium-sized, eels. The figures are consistent with the conclusion 

 that energy-rich phosphate bonds are adequate to account for the en- 

 ergy of the action potential. 



It appeared crucial to test whether or not energy-rich phosphate 

 bonds are really the energy source of ACh formation. If this be the 

 case, it would show that the energy of the primary recovery process is 

 really used for the resynthesis of the compound which, by its release, 

 supposedly initiates the nerve impulse. It would, therefore, at the 

 same time, constitute a new support for the assumption that the primary 

 "excitatory disturbance" which produces a propagated impulse may, 

 indeed, be the release of the ester. 



In confirmation of this assumption, a new enzyme, choline acetylase, 

 could be extracted from brain in cell free solution, which, under strictly 

 anaerobic conditions, in presence of adenosine triphosphate, forms 

 ACh."-3° 



The enzyme has been extracted from homogenized brain. From one 

 gram of fresh rat or guinea pig brain, enzyme solutions were obtained 

 which form 150-200 /xg. of ACh per hour. More recently, up to 250 

 ;ag./g./hr. were obtained. 



Presence of eserine and fluoride is necessary to inhibit the action of 

 cholinesterase and adenosine triphosphate, respectively. Inhibition of 

 the latter enzyme is necessary, since, otherwise, the breakdown of 

 adenosine triphosphate occurs too rapidly. Fluoride inhibits this 



