172 LEONARD NELSON 



I should like briefly to outline a frame of reference on which to hang 

 some remarks. The sperm, once launched, may be regarded as a self- 

 propelled device perhaps endowed with a guidance system sensitive 

 to external signals, such as sperm-egg interacting substances. It is 

 powered by fuel which may be continuously resynthesized at or near 

 the site of utilization, either from stored precursors or from sub- 

 stances which diffuse or are actively transported across the cell mem- 

 brane. Energy for the synthetic reactions may be derived from fructol- 

 ysis or glycolysis or by oxidation of substances such as the products 

 of phospholipid metabolism (Hartree and Mann, 1959). (There is no 

 evidence at hand that fuel may be delivered by trickling through the 

 apparently undifferentiated matrix of the flagellum or through "hol- 

 low" longitudinal tubules from fuel generators in the midpiece.) 

 Initiation of the propulsive wave may be triggered by dilution with 

 suitable media, namely seminal plasma constituents or other natural 

 or synthetic physiological solutions, which provide an adequate stim- 

 ulus even in the absence of extraneous supplemental substrate. The 

 coordination essential for effective propulsion has been postulated 

 by Bradfield (1955) as the function of a conductile system, possibly 

 the central pair of longitudinal fibers or the nine axial fibers (all of 

 which coincidentally have different solubility characteristics from 

 the nine peripheral fibers of the mammalian sperm). Once the wave 

 has been initiated in a given peripheral fiber, it continues as a suc- 

 cession of propagated localized contractions, and if each of the nine 

 peripheral fibers is contractile, the neighboring fibers sequentially 

 proceed to contract in coordinated fashion in a particular phasic re- 

 lationship. A cycle of alternating contraction and relaxation phe- 

 nomena may serve intrinsically to regulate the propagation of the 

 undulatory wave. 



I should like to consider in detail. some of these attributes of the 

 moving mammalian spermatozoon in the context of experimental 

 procedures designed to relate chemical events to specific morphologi- 

 cal characters. The presence of both adenosine triphosphate (ATP) 

 and adenosine triphosphatase (ATPase) in sperm has been known 

 since the work of Lardy and colleagues (1945), Mann (1945), Roth- 

 schild and Mann (1950), and Engelhardt (1946). During the last dec- 

 ade, evidence was obtained showing not only the ATPase (Nelson, 

 1954; Tibbs, 1957) but also succinic dehydrogenase and cytochrome 



