62 The Biochemistry of Semen 



were less harmful to motility than hypotonic media, and that the 

 relatively slight adverse effect of hypertonicity could be diminished 

 by partial replacement of sodium chloride with glucose. Further- 

 more, the extent to which a hypotonic or hypertonic medium can 

 affect the spermatozoa, very much depends on the degree of sperm 

 dilution. Highly concentrated solutions of sodium chloride incor- 

 porated in so-called salt-jellies, have been shown to possess marked 

 spermicidal properties (Gamble, 1953). 



Influence of heat and cold; sperm vitrification and 'la vie latente'' 



Temperature has long been known to exert a powerful influence in 

 determining the onset of spermatogenesis and breeding activity in 

 animals. The effect of increased temperature on the male reproduc- 

 tive organs presents many intriguing questions. Hyperpyrexia fre- 

 quently causes a temporary azoospermia in man, and a hot climate 

 is believed to be the principal cause of certain forms of subfertility 

 among domestic animals in tropical countries. Mammalian testes 

 removed from the scrotum and placed in the abdominal cavity, 

 where the temperature is a few degrees higher, cease to produce 

 spermatozoa; degeneration of the spermatogenic tissue sets in and 

 spermatogenic function is not resumed while 'experimental crypt- 

 orchidism' prevails. In the guinea-pig, a complete cessation of sper- 

 matogenesis can be brought about experimentally by scrotal appli- 

 cation of heat (6° above the normal body temperature) for a period 

 of 10 min. (Moore, 1924, 1951). A similar effect can be produced 

 in rams; semen collected from such animals a week or two later 

 contains only a small number of spermatozoa, mostly dead or 

 degenerate; the seminal plasma on the other hand, retains its 

 normal composition or shows even a slightly elevated content of 

 fructose (Glover, 1954). In bulls, heat-induced azoospermia is said 

 to be associated with an increased excretion of neutral steroids in 

 the urine (Meschaks, 1953). Cold, like heat, has an adverse effect on 

 sperm cells in vivo. An ice-pack applied for 10 min. to the testes 

 of a rabbit invariably results in disintegration of spermatozoa in 

 the epididymides (Chang, 1943). 



No less dramatic but different in kind are the in vitro effects of 

 heat and cold on spermatozoa. Dog and rabbit spermatozoa although 

 capable of survival for several hours in vitro at 40°, soon lose their 



