The Influence of Extraneous Factors 59 



and other forms of radiation in the sperm cell are by no means 

 established. The amount of information on this subject, however, is 

 steadily mounting, ever since Bohn's (1903) and Hertwig's (1911) 

 fundamental observations on the abnormal development of sea- 

 urchin and frog ova inseminated with spermatozoa previously ex- 

 posed to radium emanation. The exposure of the testes to relatively 

 small doses of X-ray results in sterility because of the extreme 

 sensitivity of the seminiferous epithelium and complete breakdown 

 of spermatogenesis; but direct irradiation of ripe, ejaculated sperma- 

 tozoa, in which the nuclei are in the resting state, has usually little 

 or no effect on motility, longevity, morphology or metabolism of 

 sperm. Nevertheless, irradiated spermatozoa are either altogether 

 infertile or, if they retain the power to penetrate the ovum and effect 

 syngamy, they are incapable of inducing normal development of the 

 ovum owing to damaged chromatin. This conclusion is the outcome 

 of extensive investigations on irradiated spermatozoa of several 

 species, including sea-urchins (Henshaw, 1940; Barron, Gasvoda 

 and Flood, 1949; Blum, 1951), frogs (Bardeen, 1907; Dalcq and 

 Simon, 1931; Rugh, 1939), insects (Barth, 1929; Eker, 1937), rats 

 (Henson, 1942; Fogg and Cowing, 1952), mice (Snell, 1935), rabbits 

 (Asdell and Warren, 1931; Amoroso and Parkes, 1947; Murphree, 

 Whitaker, Wilding and Rust, 1952), and fowl (Kosin, 1944). The 

 irradiation of cock semen in vitro with X-ray doses up to 10,000 r 

 has been shown by Kosin to have no detectable effect on the motility, 

 respiration and anaerobic glycolysis, but the fertilizing capacity of 

 these spermatozoa was markedly reduced already after exposure to 

 200 r, and was altogether destroyed after a dose of 5500 r. These 

 results serve to underline the fact that sperm fertility may react to 

 extraneous factors in a different manner from sperm motility and 

 metabolism. In our experience, ram semen irradiated with 100,000 r 

 and examined immediately after exposure, has normal motility, 

 fructolysis and adenosine triphosphate content; evidently, the X-ray 

 injury inflicted upon the spermatozoa as reflected in their diminished 

 fertilizing capacity, must be the result of some other chemical change, 

 possibly in the state of polymerization of the deoxyribonucleic acid 

 in the sperm chromatin. 



The sensitivity of the spermatogenic tissue to short-wave radiation 

 is in marked contrast to the apparent resistance of the male accessory 



