720 



SPERM, OVA, AND PREGNANCY 



TABLE 13.3 



Mineral concentrations in male reproductive fluids 



(From R. G. Cragle, G. W. Salisbury and J. H. 



Muntz, J. Dairy Sc, 41, 1273-1277, 1958.) 



plete analyses of inorganic ions in the fluids 

 of the male tract are those by Cragle, 

 Salisbury and Muntz (1958) for the testicu- 

 lar and ampullar fluids of the bull. The 

 values are compared with those of seminal 

 plasma and seminal vesicular fluid in Table 

 13.3. 



One type of epididymal reaction which 

 may be of considerable importance, al- 

 though the mechanism of the process is little 

 understood, is that concerning ionic ex- 

 change, alluded to above. Salisbury and 

 Cragle (1956) showed that shifts in the 

 sodium-potassium ratio occur in the luminal 

 contents of the goat and bull when sampled 

 at different levels of the tract. The com- 

 bined "semen" (sperm and fluid) tends to 

 show a relative increase in sodium ion and 

 an increase in K+ + Na+ when compari- 

 sons are made of tubal contents from suc- 

 cessively lower regions of the tract. Freez- 

 ing-point determinations indicated that the 

 fluid is initially hypertonic (— 0.600°C.), 

 with respect to blood, and decreases in 

 tonicity with passage through the tube. De- 

 terminations of epididymal plasma and 

 seminal plasma of ejaculated bull semen 

 tended to confirm these results with respect 

 to increase in Na+ and the combined K+ -l- 

 Na+ values (S0renson and Andersen, 1956). 



In a general way, the capacities for mo- 

 tility and fertility seem to be acquired 

 about the same time, but in neither case is 

 this brought about by a sudden change. The 

 capacity for fertilization increases as the 

 gametes are taken from more distal regions 

 of the tract. In the fowl, for example, in- 



semination with sperm from the testis, epi- 

 didymis, and vas deferens, respectively, 

 gave 1.6, 18.8, and 65.3 per cent fertile eggs 

 (Munro, 1938). Similarly, in the guinea pig, 

 sperm removed from the proximal and distal 

 portions of the epididymis and used in arti- 

 ficial insemination resulted in 33.4 and 68.0 

 per cent pregnancies (Young, 1931). After 

 ligation of the vasa deferentia and aging of 

 the sperm, the percentage of fertility from 

 proximal and distal sperm shifted to 44.2 

 and 32.5 per cent, respectively, for 20-day 

 postligation sperm, and to 49.0 and 25.0 per 

 cent for 30-day stored sperm. It seems clear 

 that, with storage, the maturation of the 

 sperm is followed by a process of senescence. 

 This was further suggested by Young's ex- 

 periments, since the percentage of aborted 

 and resorbed fetuses increased apparently 

 when fertilization was accomplished by aged 

 spermatozoa. 



Whether or not the relative fertility rates 

 of spermatozoa from different levels of the 

 male genital tract can be explained entirely 

 on the assumption that motility and fer- 

 tilizing capacity go hand in hand remains to 

 be seen, since other aspects of sperm behav- 

 ior also change with transit through the 

 ducts. Young (1929c) pointed out, for ex- 

 ample, that the heat resistance (to 46°C.) 

 of guinea pig, rat, and ram sperm decreases 

 as they migrate through the tract, and Las- 

 ley and Bogart ( 1944) showed that the re- 

 sistance of boar sperm to "cold shock" is 

 likewise reduced. 



E. THE FATE OF NONUTILIZED SPERM 

 IN THE MALE 



In the absence of ejaculation, the question 

 arises as to the fate of the millions of gam- 

 etes which are continuously generated dur- 

 ing spermatogenesis. It hacl been previously 

 assumed that sperm elimination is by "in- 

 sensible ejaculation"; sperm have been de- 

 tected in the urinary outfiow (Wilhelm and 

 Seligmann, 1937). It was shown, however, 

 by Young and Simeone (1930; Simeone and 

 Young, 1931), and since confirmed by 

 others, that the sperm of the guinea pig, for 

 example, undergo degeneration and dissolu- 

 tion within the epididymis. The disposal of 

 the degradation products of the sperm, on 

 the other hand, is not clear from these ex- 

 periments. They could very possibly be 



