252 DAVID W. BISHOP 



middle ground has been explored by leaving the contractile proteins 

 in the fibers but extracting soluble substances with the result that a 

 dead but contractile system is available for study in a relatively naked 

 state. Szent-Gyorgyi (1949) and Varga (1950) first demonstrated the 

 feasibility of preparing these glycerol-extracted models of muscle- 

 fiber bundles, and the Webers (1950) adapted the technique to single 

 muscle fibers. The preparation of extruded actomyosin thread models 

 and compressed monolayer actomyosin models was soon perfected by 

 Portzehl and Weber (1950) and Hayashi (1952). It is only fair to add 

 that, despite giant strides made in these areas of muscle research, plus 

 equally impressive advances in ultrastructural studies (see Huxley, 

 1957), a unifying theory of muscular contraction, involving activa- 

 tion, energy transfer, and mechanocoupling, has not yet been de- 

 vised (Wilkie, 1954; Pringle, 1960). 



Sperm motility studies likewise have, in large measure, advanced 

 on a triple front. Although necessarily less precise, the physiology of 

 flagellation has been defined in terms of velocity, amplitude, fre- 

 quency, and power requirements in investigations initiated by Sir 

 James Gray (1931, 1955, 1958) and discussed by others during this 

 symposium. Significantly lacking, however, are data concerning 

 changes in action potential or other detectable charge characteristics 

 of spermatozoa during the flagellation cycle. On the other hand, the 

 extraction of musclelike sperm adenosine triphosphatases (ATPases) 

 is an established fact and, while the enzymes' characteristics and 

 vital role have been only partially elucidated, they have been im- 

 mortalized, in one species at least, by virtue of the distinction of 

 having been named "spermosin" (Engelhardt, 1946). While essen- 

 tially like myosin in respect to many properties (Bishop, 1962), the 

 extractable sperm contractile proteins, at least of lower vertebrates, 

 behave like actomyosin-type proteins (see Pautard, this symposium). 

 An actinlike moiety has reportedly been isolated from sea urchin 

 spermatozoa by A. Ruby (personal communication). The third al- 

 ternative procedural pathway in the study of sperm motility, the 

 preparation and activation of flagellar models, is the one to be pur- 

 sued here, since the results seem relatively clear-cut even though the 

 interpretations may be limited. 



Parenthetically, the designation of these preparations as models is 

 consistent with the term as used by Szent-Gyorgyi and others in re- 



