754 



SPERM, OVA, AND PREGNANCY 



chemical nature of these longitudinal fila- 

 ments, their proximal association with yet 

 another array of 9 peripheral fibers, their 

 relation to the matrix of the flagellum, and 

 their relation to one another, are described 

 elsewhere in considerable detail (Bishop, 

 1961 ) . As a general conclusion, the three 

 main divisions of sperm into head, middle 

 piece, and tail correspond roughly to their 

 genetic, metabolic, and motile functions. 



B. BIOCHEMICAL FEATURES 



The availability and homogeneity of sper- 

 matozoa have long appealed to the biochem- 

 ist in choosing a cell tyjie for study. Both 

 chemical and histochemical methods have 

 been employed in investigations of the com- 

 position of sperm, and recent developments 

 in quantitative cytochemistry show good 

 agreement in the results obtained by the two 

 general procedures. Complete analyses of the 

 chemical components of several types of 

 spermatozoa are now available and include 

 the full range of substances from ions to en- 

 zymes, many of which have been roughly 

 localized within the major regions of the 

 cells. For more extensive treatment concern- 



FiG. 13.17^. Highly diagrammatic representation 

 of transverse sections of sperm flagellum and cil- 

 ium ; 2 central and 9 double peripheral fibrils typi- 

 cal of all such motile organelles. Mitochondria 

 (oblique hatching) present in midpiece. An addi- 

 tional array of 9 outermost filaments (solid) in the 

 midpiece of mammalian sperm extends into the 

 proximal portion of the flagellum. The fibrous 

 sheath of the tail is frequently ribbed as indicated. 



Fig. 13.17fi. Diagram of rat sperm tail at various 

 levels from midpiece (A) to tip (G). Note bilateral 

 symmetry of fibrillar arrangement and termination 

 of outer longitudinal fibers at different levels of 

 flagellum. (Courtesy of D. W. Fawcett.) 



ing the functional composition of sperm, the 

 reader is referred to several reviews (Marza, 

 1930; van Duijn, 1954; :Mann, 1954; Bishop, 

 1961 ) ; only selected features of the volumi- 

 nous literature will be noted here. 



Just short of a century ago, Miescher, and 

 later Kossel, and their co-workers took up 

 the study of the basic proteins — protamines 

 and histones — of fish sperm nuclei, easily 

 procurable by plasmolysis of the cytoplasm 

 and collection of the heads by centrifuga- 

 tion. Progress was rapid and by the 1920's 

 more was known, it was claimed, about the 

 chemistry of the spermatozoon than about 

 any other cell (Marshall, 1922). These early 

 studies have expanded into investigations of 

 the basic proteins as conjugates with desoxy- 

 ribonucleic acid (DNA), and particular at- 

 tention has been directed toward the sig- 

 nificant and systematic changes from the 

 histone- to the protamine-type protein dur- 

 ing sperm differentiation (Miescher, 1897; 

 Kossel, 1928; Mirsky and Pollister, 1942; 



