Fertilizing capacity of spermatozoa following cold treatment of the scrotal testes of rabbits.

The fertility or sterility of a male depends on several factors, among which are the chemical constituents of the semen, the number, morphological integrity, motility, metabolism and viability of the spermatozoa. These factors, of course, are interrelated in effecting fertility or probability of fertilization. Although in normal matings the number of spermatozoa in the ejaculate is much greater than the minimum required for fertilization, it was demonstrated by Walton (1927), and by Rowlands (1944), that fertility in the rabbit was reduced if the number of spermatozoa inseminated was less than 1 million, and that sterility occurred if the number of spermatozoa was less than o-i million. Therefore, in the practice of artificial insemination in animal husbandry, the importance to be attached to the number^ of spermatozoa used is stressed by all workers (Walton, 1933; Lambert & McKenzie, 1940). In relation to fertility and sterility, the importance of sperm morphology, and the percentage of abnormal forms in the ejaculate have been emphasized by many workers (Williams & Savage (1925) and LagerlCf (1936) on bulls; Gunn, Sanders & Granger (1942) on rams), and especially by human gynaecologists (Meaker, 1934; •Moench, 1936; Lane-Roberts, Sharman, Walker & Wiesner, 1939). A percentage of abnormal spermatozoa in the semen higher than 20 is ordinarily considered liable to cause partial fertility or sterility. Data that support this statement are based upon clinical observation rather than on experiments.