CATALYSIS: THE GUIDE OF LIFE 121 



enced, by exceedingly minute proportions of highly specific sub- 

 stances, even though the actual number of molecules (or other 

 particulate units) involved may be enormous. Some activators 

 come from outside the organism, e.g., vitamins from food, trace 

 substances from the soil; others are formed within the organism, 

 e.g., auxins in plants, hormones and neurohumors in animals. 



Electric phenomena are associated with the functioning of ner- 

 vous and muscular tissue. Electrocardiograms from the heart 

 muscle and electroencephalograms from the brain are routine pre- 

 cedures in many hospitals. Sir Edgar A. Adrian (Nobel prize, 

 1932) and his collaborators measured the tiny electric impulses 

 passing along nerves. 52 Herbert S. Gasser and Joseph Erlanger 

 (Nobel prize jointly, 1944) applied the oscillograph to demonstrate 

 the details of these impulses. Based on interpretations of experi- 

 mental work of Elliot, Howells, Dixon, Otto Loewi (Nobel prize, 

 1936), W. A. Cannon and Sir H. H. Dale (Nobel prize, 1936), it 

 has for many years been thought that nerves act upon effector 

 organs (e.g., muscles and other nerve cells) by releasing at the 

 nerve endings chemical substances (e.g., acetylcholine, sympathin, 

 adrenaline) which exert a stimulating or an inhibiting effect at 

 their place of liberation. These views were based on experiments 

 showing the pharmacological effects of acetylcholine, and a demon- 

 stration of its presence, under certain conditions, in the perfusion 

 fluid after stimulation. 



The new concept is based on studies of the enzymic catalysts 

 which form and break down acetylcholine, and on the correlation 

 of these reactions with the physical happenings in the living cell. 

 Quite a variety of recent experimental data indicate that the 

 propagating agent along nerves and muscle fibers, as well as across 

 nerve synapses and neuromuscular junctions, is a flow of current 

 — the action potential. However, acetylcholine plays an essential 

 role in the alteration of the surface membrane (the "progressive 

 disturbance" of Keith Lucas), permitting the flow of current. The 

 following abstract was kindly prepared for me by Professor David 

 Nachmansohn of Columbia University, who has done so much to 

 establish the new view. 



"The enzyme which inactivates acetylcholine by splitting the active 

 ester into its inactive compounds, choline and acetate, is cho- 

 linesterase. One of the most essential features resulting from studies 

 of this enzyme is the high speed with which acetylcholine may be in- 

 activated. This speed parallels that of the electrical manifestations, 



