712 



SPERM, OVA, AND PREGNANCY 



tract is, from the sperm's viewpoint, in the 

 main a passive process (Simeone, 1933). 

 The mechanism by which they are moved 

 along the duct system, however, is not well 

 understood; the mechanics may well vary 

 in different segments. Certain workers have 

 emphasized the currents of fluid which could 

 sweep the sperm out of the seminiferous 

 tubules and into the efferent ducts and epi- 

 didymis (see Young, 1933; Macmillan, 

 1953). Resorption of fluid by the efferent 

 ducts (Young, 1933; Ladman and Young, 



1958) or cpididymal epithelium (Mason and 

 Shaver, 1952; Cleland, Jones and Reid, 



1959) would complete the fluid circuit and 

 simultaneously concentrate the sperm mass 

 in the distal reaches of the duct system. 

 Certain ligation experiments in which the 

 male ducts were occluded at various levels 

 tend to support this concept of transport by 

 fluid currents, and circumstantial evidence 

 is further afforded by the presence of motile 

 cilia in the upper segment of the genital 

 tract. On the other hand, other experiments 

 which involved separation of the testis from 

 the efferent ducts, thereby cutting off the 

 supply of fluid, demonstrate unequivocally 

 that the sperm, under these circumstances, 

 are carried distally by some other means of 

 tubal transport (Young, 1933; Macmillan 

 and Harrison, 1955). 



More recently acquired evidence indicates 

 that muscular activity may play the pre- 

 dominant role in sperm transport through 

 the male ducts. Roosen-Runge (1951) has 

 observed movement in the seminiferous tu- 

 bules of the dog and rat, both in the intact 

 testis and in vitro in physiologic saline at 

 36° C. The undulating motion was attrib- 

 uted, by Roosen-Runge, to the contraction 

 and relaxation of the Sertoli cells within 

 the tubules. A more plausible explanation 

 may rest in Clermont's recent (1958) elec- 

 tron micrographic demonstration of fibrous 

 elements which lie in the wall of the seminif- 

 erous tubule of the rat and seem to re- 

 semble smooth muscle cells. 



The ductuli efferentes of the adult rat can 

 be cultured successfully in roller-tube tis- 

 sue-culture preparations (Battaglia, 1958). 

 Tubules maintained as long as 12 days show 

 spontaneous movement, presumably due to 

 muscular contractions. This activity could 



provide a mechanism whereby spermatozoa 

 are carried along these ducts, in vivo. 



Migration of spermatozoa through the 

 epididymis proper is mainly, although per- 

 haps not exclusively, brought about by 

 spontaneous peristaltic and segmental 

 movements of the duct. Such activity was 

 first clearly shown in the guinea pig by 

 Simeone (1933) and in the rat by Muratori 

 (1953) and has been confirmed and recorded 

 cinematographically by Risley (1958, 1960). 

 Rhythmic contractions sweep along the 

 adult tubule at regular intervals of 7 or 8 

 seconds. After gonadectomy, contractions 

 continue in the mature duct for two more 

 weeks. Hypophysectomy results in the loss 

 of activity within 10 days in the head, and 

 within 13 days in the body and tail of the 

 epididymis. In tissue-culture preparations, 

 the spontaneous movement of the epididy- 

 mis also continues for some time (12 days), 

 the activity being the same whether the 

 ducts are excised from normal or from gon- 

 adectomized rats (Battaglia, 1958). It is of 

 some historic interest to note that Moore 

 and Quick, as early as 1924, suggested a 

 neuromuscular mechanism for epididymal 

 sperm transport as a result of their studies 

 on vasectomized rabbits; at the same time 

 they refuted the then hotly contested claims 

 of Steinach and others that vasectomy re- 

 ults in seminiferous atrophy and interstitial 

 hypertrophy. Complete occlusion of the rat 

 vasa eff'erentia, on the other hand, is claimed 

 to lead invariably to si^crmatogenic destruc- 

 tion (Harrison, 1953). 



Transport through the epididymis re- 

 quires 2 to 4 days in the fowl, 4 to 7 days 

 in the rabbit, 9 to 14 in the ram, 14 to 

 18 in the guinea pig, 8 in the mouse, about 

 15 in the rat, and 19 to 23 days in man 

 (Toothill and Young, 1931; Munro, 1938; 

 Edwards, 1939; Brown, 1943; MacMillan 

 and Harrison, 1955; Asdell, 1946; Dawson, 

 1958; Oakberg and DiMinno, 1960). The 

 guinea pig determinations of Toothill and 

 Young (1931 ) made use of the migration of 

 India ink particles, injected into the head 

 of the epididymis, and not of sperm trans- 

 port per se. The apparently rapid rate of 

 migration of sperm in the fowl may be at- 

 tributed to the relatively short length of the 

 epididymis (Munro, 1938). Isolation of the 



