CYTOCHEMICAL ASPECTS 173 



oxidase (Nelson, 1955) to be concentrated in almost equal propor- 

 tions in the midpiece and tail (Fig. 1). This does no violence to Gray's 

 postulate (1928, p. 49) that a "moving wave cannot provide energy 

 for propelling an organism and at the same time pass on with un- 

 reduced amplitude unless the energy being lost is continually being 

 replaced as the waves move along." In a theoretical analysis of wave 

 propagation along flagella, Machin (1958) has demonstrated that 

 some of the energy fed into each element of the flagellum will be 

 used to overcome viscous forces of the medium and that the re- 

 mainder of the energy is absorbed in elastic deformation of the ele- 

 ment. Unless a reversible mechanism exists to convert the elastic 

 energy back into chemical energy, it is irrecoverable and will de- 

 grade into heat in the elastic or contractile components. 



The application of cytochemical techniques to frozen-dried ma- 

 terial subsequently processed for electron microscopy has now made 

 it possible to substantiate, with a somewhat higher degree of resolu- 

 tion, the data obtained from isolated sperm fragments. The coinci- 

 dence of distribution of enzymes concerned with the utilization and 

 resynthesis of ATP establishes the rationale for ascribing the genera- 

 tion of the undulatory wave to the flagellum itself (Nelson, 1958a, 

 1959b) (see Figs. 2 and 3). Enough ATP may be resynthesized via 

 oxidative phosphorylations at the disposal of the flagellum (Nelson, 

 1958b) so that the mechanical reconversion of the energy of deforma- 

 tion into chemical energy need not be limiting (even when the power 

 expended amounts to 2 X 10~ 7 erg /sec, as noted by Rothschild at 

 this symposium). 



If the peripheral fibers are contractile structures responsible for 

 propulsion of the sperm, then, according to Cleland and Rothschild 

 (1959), they may be regarded as tensile elements; parts of the fibrous 

 "spiral" sheath may consist of compression elements which become 

 deformed as the peripheral fibers contract. Electron micrographs 

 (Fig. 4) of frozen-dried rat sperm may offer a clue to the site and 

 nature of the deformations. Since, of course, the peripheral fibers 

 themselves are deformed in the course of their undulations, Machin 

 (1958) proposes that the amplitude of the wave could be sustained 

 by energy arising in the more distal elements, activated as a result of 

 the "passively propagated" bending wave. This limitation of the "ac- 

 tively induced bending" to the proximal end of the flagellum would 



