576 ANNALS NEW YORK ACADEMY OF SCIENCES 



Tlie action potential, for example, may not represent a passive de- 

 polarization but a potential actively produced by the chemical reac- 

 tions. But whatever the details, it is highly probable that the nerve 

 impulse consists basically of a local membrane change of a chemical 

 and physical nature, which leads to a flow of ions, or current, which 

 in turn starts the local membrane change at adjacent points" (p. 64^). 



"... Either the same kind of ion migration and chemical response 

 which represents successive activation of one region of the nerve fibre 

 by another must also take place at the synapse, or it is conceivable 

 that the end of the axone acts as a miniature gland and, when stim- 

 ulated, produces some chemical which is able to excite an adjacent or 

 neighboring dendrite" (p. 74^) . 



"In the nervous system itself, a similar mechanism has been consid- 

 ered by several workers. The end of an axone is at least an unspecial- 

 ized end organ, often a complicated one (as, for example, in the olfac- 

 tory glomeruli) and might activate the dendrite or cell body on which 

 it impinges via chemical as well as electrical changes. The transmis- 

 sion from cell to cell by means of action potentials has long been the 

 orthodox view, and emphasis on the chemical possibilities has had a 

 novel flavor. In fact, however, the conduction along a nerve fibre 

 involves excitation of a resting region by an active one, and both elec- 

 trical and chemical components are present in the mechanism of propa- 

 gation. At the ending, which is specialized, at least anatomically, 

 either or both components might well be exaggerated to facilitate trans- 

 mission over a critical region. Long-enduring action or depolarization 

 potentials or special chemical accumulation might equally well be 

 utilized in various situations and (except for familiarity with the one 

 idea) one seems as likely as the other" (p. 546^) . 



GENERAL BACKGROUND 



The Role of Metabolism 



Nerve fibers, like whole neurones or any other cells, depend on a 

 maintained metabolism to survive and to function. This was strongly 

 indicated when it was found,'* near the start of this century, that nerve 

 conduction failed in the absence of oxygen; and was proved when 

 nerve respiration and heat production, at rest and on activity, were 

 successfully measured by several workers in the mid-twenties.'"*- ^ The 

 next question is: For what result is metabolism essential? Or, What 

 agencies link the chemical reactions with the physiological conse- 

 quences? In general, the answer is clear enough: Metabolism liberates 



