94 The Biochemistry of Semen 



a fairly stable colloidal suspension with dilute serum, whereas 

 depolymerized hyaluronate under identical conditions remains clear; 

 the 'viscosity reduction (v.r.)' method measures the decline in vis- 

 cosity caused by depolymerization; in the so-called 'Spinnbarkeit'- 

 method the stringiness of hyaluronic acid is assessed by means of 

 a special device, before and after enzymic treatment. Each of the 

 above methods, however, is open to criticism and limited in its 

 scope (cf. Lundquist, 1949a; Swyer and Emmens, 1947; Meyer and 

 Rapport, 1952). 



The mammalian testis and sperm are the richest animal sources 

 of hyaluronidase. The existence in testes and spermatozoa of a 

 'spreading' or 'diffusing' factor which, when injected intradermally, 

 increases the permeability of the skin to fluids, was established by 

 Hoff'man and Duran-Reynals (1931) and McClean (1930, 1931); but 

 Chain and Duthie (1939, 1940) deserve the credit for being the first 

 to show that purified preparations of the testicular spreading factor 

 possess strong hyaluronidase activity. Their finding was soon con- 

 firmed by other workers who made several attempts to purify the 

 enzyme (Hahn, 1943; Freeman, Anderson, Webster and Dorfman, 

 1950; Tint and Bogash, 1950). The best preparations of bovine 

 testicular hyaluronidase so far available are over ten thousand times 

 more active than the testicular tissue itself, but as yet, even the most 

 highly purified enzyme does not appear to be a homogeneous protein. 



Hyaluronidase originates in the seminiferous epithelium of the 

 mature testis, and in semen it is associated with the spermatozoa and 

 not with the seminal plasma (Werthessen, Berman, Greenburg and 

 Gargill, 1945; Joel and Eichenberger, 1945; Kurzrok, Leonard and 

 Conrad, 1946; Swyer, 1947^; Jacquet, Plessis and Cassou, 1951). 

 The content of hyaluronidase per sperm cell is highest in rabbit and 

 bull; there is less of it in human and boar sperm, very little in dog, 

 and practically none in birds and reptiles. 



Although it is actually a part of the sperm cell, hyaluronidase is 

 nevertheless so readily released by spermatozoa into the surround- 

 ing medium that it must be assumed to be located somewhere very 

 close to the cell surface, possibly on the sperm-head (Hechter and 

 Hadidian, 1947; Johnston and Mixner, 1947; Perlman, Leonard 

 and Kurzrok, 1948). A few hours' freezing of an aqueous sperm 

 suspension at -10^, or 24 hours' standing at 0°, has been found by 



