GERARD: NERVE METABOLISM AND FUNCTION 595 



tense. But is the chemical ACh? Quien sabef It should be recalled 

 that undrugged nerve also has an enduring after-potential, which can 

 increase in intensity for several minutes and persist for ten or more. 



40 



CONCLUSION 



Dr. Nachmansohn skillfully and generously organized the extraor- 

 dinarily successful conference of which this is the result, to bring forth 

 much current evidence and a full range of judgments bearing on the 

 significance of ACh, as well as of electrical changes, for the functioning 

 of nerve and other tissues. With these facts and arguments before us, 

 we must conclude that ACh is not critically involved in nerve conduc- 

 tion, and we must be reserved in assigning it a role in junctional trans- 

 mission, particularly within the nervous system. This is progress and 

 should lead to greater progress. Our thinking and our consequent ex- 

 perimentation now can be directed along new lines. 



This is not to say that the hypotheses which must be relinquished 

 have been worthless, nor that the ACh system is unimportant. Hy- 

 potheses are not true or false (who can assert absolute truth?) ; they 

 are useful or useless. They do or do not suggest investigations which 

 reveal new facts, facts which discriminate between alternate views or 

 which fill in gaps of felt ignorance or which suggest new interpretations 

 and experiments. By such standards, the various ACh hypotheses have 

 been good ; they have been abundantly fruitful. But this fruit is ripe, 

 and it is time for the seed of a new idea to be germinated. Fresh fruit 

 will then ripen with time and the present crop not be husbanded until 

 it rots or dries up. 



What a new and fertile approach may be, I do not know. ACh and 

 the enzymes that operate in the system can hardly be present adven- 

 titiously. Nature no more evolved the ACh system to mislead bio- 

 chemists than it evolved the giant nerve fiber to aid physiologists. ACh 

 has some significance to cells. Perhaps this system is a fragment of a 

 universally important metabolic mechanism, dealing, if one must hazard 

 a particular guess, with the manipulation of lipid molecules. Such facts 

 or statements as the following maj'- serve as clues. ACh prevents the 

 splitting of CrP by muscle juice ;^°- choline lack increases the turnover 

 of phosphohpids;^°^ ACh can replace Ca in enabhng myosin to split 

 ^'pp.52 ^Qi^ jg |.j-jg Qj^jy system able to capture energy via both respira- 

 tory and glycolytic reactions,^^ and so is related to both respiration 

 and carbohydrate utilization rates. ^°*' "^ It would still be possible for 

 evolution to have selected this fragment of a more general system for 

 special emphasis and functioning in particular situations; to serve, for 



