Sovie Physical Properties of Protoplasm 263 



closer analogy is to be found in the rhythm of nerve conduction where 

 a cycle of oxidation-reduction reactions is assumed to pass along 

 the nerve. 



The occurrence of autocyclic chemical reactions in protoplasm is 

 not at all unlikely, but it seems more probable that the rhythm of 

 protoplasmic flow is a visible expression of a rhythmicity which 

 exists in the vital mechanism and not in the supply of energy. The 

 living mechanism may show perfect rhythm even though the source 

 of energy is in no way rhythmic. Just what rhythmic control in a 

 vital mechanism means is as yet unknown. 



In this connection the conclusion of Kamiya is important (p. 242) , 

 that "views which postulate a possible physical or chemical change 

 accompanying the change in distribution of protoplasm as the cause 

 of the reversal may be discarded," because the rhythmic motive 

 force does not disappear when the streaming is artificially stopped 

 for a time. 



In closing this chapter, I wish to give some indication of the 

 widespread occurrence of rhythmic contractility in living matter. 

 Heart muscles contract rhythmically. The muscles of the diaphragm 

 are induced to do so. Contractility occurs periodically as peristalsis 

 in the walls of the intestines, the ureter, the uterus, and the Fallopian 

 tube. Feeble rhythmic uterine contractility is by some thought 

 to be continuous. Voluntary muscles are likewise believed to 

 undergo rhythmic contractility during periods of apparent rest. The 

 bladder, not functionally contractile, can be experimentally made to 

 pulsate rhythmically. 



Rhythm in the nervous control of organisms has long been known 

 and has received added confirmation of late in work involving the 

 electric recording of rhythmic waves from the brain. -^ That a 

 rhythmic train of events in the nervous system regulates certain 

 body functions is shown by the rhythmic movement of the respira- 

 tory muscles which is not intrinsic, as in the case of the heart. Such 

 induced rhythms are controlled by periodically recurring stimuli 

 from, the medulla. When the action of a single neuron is obtained, 

 a clear record of periodic neural impulses is obtained, which recur 

 in perfect rhythm.-- 



The references so far, other than that of slime molds, have had 

 to do with mukicellular organisms, with tissues; but individual cells. 



;' Science, 81, 597. 1935. 



"'Chemistry and Medicine. Minneapolis, p. 261. 1940. 



