126 The Biochemistry of Semen 



treatment, more lipid was found in the tails (23%) than in the mid- 

 pieces (6%) or heads (7%). 



The lipid capsule 



It is probable that the high lipid content of spermatozoa is due 

 largely to the lipid 'sheath' or 'capsule' which encloses the sperm 

 cell. So it would seem at any rate, from histochemical studies, 

 including the extensive investigation of Popa and Marza (1931) who 

 described the so-called manteau Upidique in the spermatozoon of 

 man, dog, bull, ram, boar, rabbit, guinea-pig and cock. The lipid 

 capsule is presumably of importance to the spermatozoa in their 

 function, perhaps to ward off the effects of the acid vaginal milieu as 

 has been suggested by Redenz (1924). It appears to consist largely 

 of a lipoprotein complex which is fairly soluble in aqueous solvents. 

 In the case of mammalian spermatozoa, this complex has been 

 extracted with a 01 4m solution of sodium chloride at pH 9 (Dallam 

 and Thomas, 1952). In the middle-piece lipids were shown to be 

 associated with the 'spiral body' which surrounds the axial proto- 

 plasmic thread, and is derived from the mitochondria of the sperma- 

 tids (Wislocki, 1950; Brown, 1952). 



Acetal phospholipids or plasmalogens 



An interesting feature of the sperm cell is a characteristically high 

 content of acetal phospholipids or plasmalogens. Feulgen and 

 Rosenbeck (1924) while studying the 'nucleal' reaction of human 

 spermatozoa, noted that when fresh smears of human semen were 

 treated with Schiff's fuchsin-sulphurous acid reagent, the middle- 

 pieces and tails, though devoid ojf nuclear material, stained strongly. 

 This observation was followed by a demonstration that cells in 

 general contain in their protoplasm some material which stains 

 diffusely with Schiff's reagent, but differs from nucleoproteins by its 

 solubility in ethanol. The name 'plasmal' was bestowed upon this 

 material, which was shown in subsequent investigations by Feulgen 

 and his co-workers to arise from 'plasmalogen', a group of peculiar 

 phospholipids widely distributed in tissues, and distinguished by the 

 presence of higher fatty aldehydes in place of the usual fatty acids. 

 The plasmalogen isolated by Feulgen and Bersin (1939) from beef 

 muscle was identified as an acetal of glycerylphosphorylcolamine. 



