154 The Structure of Protoplasm 



substance which closely resembles myosin with reference to its 

 general chemical properties. 



One cannot overlook the fact, however, that pressure also may 

 induce marked changes in other types of metabolic reactions in the 

 cell. Fontaine ('28) , for example, reports increased oxygen con- 

 sumption in a number of small marine animals exposed to pressure 

 in the range up to about 1,500 Ibs./in.,- and Deuticke and Ebbecke 

 ('37) describe a greatly accelerated breakdown of phosphocreatin 

 and an increased lactic acid production in frog skeletal muscle during 

 a short period of tetanic contraction at 8,000 lbs. Furthermore, it is 

 well known that a great variety of organic reactions are markedly 

 affected as to rate, and as to the point of equilibrium, by pressures 

 within and beyond the physiological range (see, for example, Faw- 

 cett and Gibson, '34) . 



B. RELATION BETWEEN GELATION AND THE PHYSIOLOGICAL RESPONSE 



In seeking fundamental factors which may explain why in one 

 group of physiological activities (amoeboid movement, cyclosis, cell 

 division, and pigmentary responses) the inhibition imposed by 

 pressure is continuously in proportion to solation throughout all of 

 the pressure range, whereas this is not the case for a second group 

 (contraction of muscle, conduction of nerve, and the motility of cilia 

 and flagella) , two questions may be raised. (1) Is it true, perhaps, 

 that gelation reactions are directly concerned in the development 

 of the mechanical energy in the first group of responses but are not 

 concerned, at least directly, in the second; or (2) is it possible that 

 gelation, reactions are involved in both cases but that the metabolic 

 reactions which precede the active response and provide energy for 

 it are relatively immune to augmentation by pressure in the first 

 group, but not immune in the second? 



An affirmative answer to the first question would provide the 

 basis for a simpler working hypothesis. However, the data of Brown 

 ('34b and '36) , which indicate that augmented tension in muscle 

 depends upon a greater mobilization of energy prior to the actual 

 contraction and that the contractile process itself is actually 

 depressed even by relatively low pressure, make it doubtful that 

 this more restricted view is entirely tenable. In any event, however, 

 in view of the accumulated data, one can scarcely avoid the conclu- 

 sion that gelation reactions are directly concerned in the develop- 

 ment of mechanical energy, at least in one group of physiological 



