ABSTRACT
The effect of temperature on spermatogenesis and on spermatozoa in mammals is very distinctive. Testicular temperature is a few degrees below body temperature, 1·5–2·5°C. lower in rabbits, 2·0–3·5° C. in guinea-pigs, 4–8° C. in rats (Moore & Quick, 1924), 4–9° C. in rams (Phillips & McKenzie, 1934). Spermatogenesis is retarded or even completely stopped by increasing the normal temperature of the testis, as for example by natural and artificial cryptorchidism (Moore, 1922, 1924 a, rats and guinea-pigs) or by applying heat to the testis (Fukui, 1923a, rabbits; Moore, 1924b, guinea-pigs; Young, 1927, guinea-pigs ; Phillips & McKenzie, 1934, rams ; Macleod & Hotchkiss, 1941, human). An optimum temperature, a few degrees below that of the body, can therefore be postulated for spermatogenesis. Although the contraction and relaxation of the scrotum in response to the outside temperature can bring about thermo-regulation of the testes by both raising and lowering the temperature as suggested by Crew (1922), and this mechanism undoubtedly plays a part in reducing temperature, no ill effect on spermatogenesis of lowering the temperature below the optimum has-been found even when the testes of rats were subjected to a temperature as low as 6–8° C. (Phillips & McKenzie, 1934). It may be that spermatogenesis is less susceptible to injury at a lower than at a higher than normal temperature.
