280 TERU HAYASHI 



muscle," if you wish. The point is that they are not living muscle, 

 and the reactions and characteristics of a simplified system are not 

 necessarily those which prevail in vivo. For example, there is wide- 

 spread acceptance that muscle contraction is accompanied by the en- 

 zymatic splitting of ATP, and relaxation by the nonsplitting of ATP, 

 a belief sustained by data from test-tube studies. But from living 

 muscle studies there is no evidence to support this, and, in fact, the 

 data of Chance (1959) and his collaborators demonstrate that in the 

 course of a twitch not nearly enough ATP is split to account for the 

 energy expressed by the muscle. I am not suggesting that the ATPase 

 concept is incorrect, but only that it is not a proved in vivo fact, in 

 spite of its wide acceptance. 



The foregoing cautionary statement applies to all information 

 from inanimate systems; thus, there is no proof of the existence of an 

 in vivo relaxing factor, for example. There is, of course, a real value 

 in studying simplified systems, and I do not mean to discourage this 

 line of research but only to caution against the tendency to transfer 

 without reservation results of such research to living muscle or living 

 sperm. 



We may move now from these general considerations to a more 

 specific case where information from muscle research must be re- 

 garded with caution by the participants of this symposium, for the 

 authors of the papers have enunciated two mechanisms of flagellar 

 movement derived from muscle study. The first, as expressed by both 

 Tibbs and Bishop at this symposium, calls for localized, propagated 

 contractions and accompanying relaxations in the flagellar structure. 

 The second, suggested by Brokaw (this symposium), involves active 

 contraction of the flagellum coupled by feedback to internal viscosity 

 and/or elasticity to give oscillatory movement. The first requires re- 

 laxation as a process, either the opposite of the contraction process or 

 an entirely separate and new process which restores the contractile 

 elements to their original state. The second does not need this; all 

 that it requires is a cessation of the contractile process and one fur- 

 ther condition, namely, that the contractile structures become more 

 extensible after the cessation of the contraction process. 



The question whether or not relaxation as a process exists in sper- 

 matozoa could resolve into whether or not a "relaxing factor" exists 

 in flagella, and therefore merits discussion of the "relaxing factor" 



