WITHIN MALE REPRODUCTIVE STRUCTURES 181 



not a major factor in sperm passage along the epididymal portion of the 

 reproductive duct, as conditions within the duct appear to suppress this mo- 

 tility. It has been shown, for example (Hartman, '39, p. 681), that sperm 

 motility increases for trout sperm at a pH of 7.0 to 8.0, in the mammals a pH 

 of a little over 7.0 seems optimum for motility for most species, while in the 

 rooster a pH of 7.6 to 8.0 stimulates sperm movements. On the other hand, 

 an increase of the CO, concentration of the medium raises the hydrogen ion 

 concentration of the suspension. The latter condition suppresses sperm mo- 

 tility and increases the life of sea-urchin sperm (Cohn, '17, '18). These facts 

 relative to the influence of pH on the motility of sperm suggest that motiUty 

 during the slow and relatively long epididymal journey — a journey which may 

 take weeks — apparently is inhibited by the production of carbon dioxide by 

 the large aggregate of sperm within the lumen of the epididymal duct, a con- 

 dition which serves to keep the spermatic fluid on the acid side. This sup- 

 pressed activity of the sperm in turn increases their longevity. The matter of 

 sperm motility within the epididymal duct, however, needs more study before 

 definite conclusions can be reached relative to the actual presence or absence 

 of motility. 



2) Importance of Muscle Contraction, Particularly of the Vas Deferens. 

 If sperm are relatively immobilized during their passage through the epididymal 

 duct by the accumulation of carbon dioxide, we must assume that their 

 transport through this area is due mainly to the activities of the accessory; 

 structures together with some pressure from testicular secretion and efferent- 

 ductule activity as mentioned above. Aside from the forward propulsion re- 

 sulting from the accumulation of glandular secretion within the epididymal: 

 duct, muscle contraction appears to be the main factor involved in effecting 

 this transport. The epididymal musculature is not well developed, and muscle 

 contraction in this area may be effective but not pronounced. However, added 

 to the contracture of the epididymal musculature is the contraction of the 

 well-developed musculature of the vas deferens (fig. 100). During sexual 

 stimulation this organ contracts vigorously, producing strong peristaltic waves 

 which move caudally along the duct. The activity of the vas deferens may 

 be regarded as a kind of "pump action" which produces suction sufficient to 

 move the seminal fluid from the caudal portions of the epididymis, i.e., from 

 the Cauda epididymidis into the vas deferens where it is propelled toward the 

 external orifice. Furthermore, the removal of materials from the cauda epi- 

 didymidis would tend to aid the movement of the entire contents of the 

 epididymal duct forward toward the cauda epididymidis. From this point of 

 view, the vas deferens is an efficient organ for sperm transport, while the 

 epididymal duct functions as a nursery and a "storage organ" for the sperm 

 (see Chap. 1). Some sperm also are stored in the ampullary portion of the 

 vas deferens (fig. 101 ), but this storage is of secondary importance inasmuch 

 as sperm do not retain their viability in this area over extended periods of time. 



