BIOLOGY OF SPERMATOZOA 



715 



told, the epididymis is an imposing duct, a 

 single continuous tube about 10 feet long in 

 the guinea pig and up to 280 feet in the 

 stallion (Ghetie, 1939; Maneely, 1959). 



An impressive series of contributions per- 

 taining to the regional differentiation and 

 histology of the rat epididymis has been 

 published by Reid (1958, 1959) and Reid 

 and Cleland (1957), of the University of 

 Sydney. They divide the rat epididymis 

 into six discrete zones, plus the rete and 

 efferent ducts, on the basis of cell type. The 

 efferent ducts and zones 1 to 4 constitute 

 the head, part of zone 4, the isthmus, and 

 zones 5 and 6, the tail of the epididymis 

 (Fig. 13.1). The relative lengths and di- 

 ameters of the successive zones and the 

 cellular types are represented in Figure 

 13.2. Six major cell types are discernible: 

 principal, basal, ciliated, apical, halo, and 

 clear cells (Fig. 13.3). Ciliated cells are 

 confined to the efferent ducts — "the most 

 beautiful ciliated cells of the vertebrate 

 body" <von Lenhossek, 1898). Much of the 

 remainder of the epididymis is lined with 

 prominent, nonmotile stereocilia (Reid and 

 Cleland, 1957). Fluid resorption from the 

 lumen is pronounced in zone 4 (Cleland, 

 Jones and Reid, 1959). The principal fea- 

 tures of epididymal histogenesis in the rat 

 are summarized in Table 13.2. During the 

 first three weeks of postnatal development, 

 the epididymis remains in an vmdifferen- 

 tiated state. At about four weeks, differ- 

 entiation is first noted in the head of the 

 epididymis and is completed by day 37. 

 Differentiation of the tail begins later than 

 that of the head and is completed only at 14 

 weeks of age. Sperm are first found in the 

 testis at 8 weeks and appear in the epi- 

 didymis 2 weeks later. 



The epididymis, like the accessory repro- 

 ductive glands, responds to changes in cir- 

 culating androgen, and its normal histo- 

 logic integrity also is apparently dependent 

 on the male hormone (Maneely, 1959) . Cas- 

 tration is followed by reduction in tubal di- 

 ameter and loss of specific cellular compo- 

 nents (Cavazos, 1958; Maneely, 1958). Acid 

 and alkaline phosphatase activities of the 

 mouse epididymis decrease after gonadec- 

 tomy (Allen and Slater, 1957, 1958). Intra- 

 cellular polysaccharides, visualized by the 



Fig. 13.1. Right testis and epididymis of rat 

 viewed from (A) lateral and (B) medial aspects; 

 cranial end uppermost. Small circles, efferent ducts; 

 crosses, coni vasculosi ; coarse dots, zone 1 ; oblique 

 hatching, zone 2; fine horizontal hatching, zone 3; 

 coarse horizontal hatching, zone 4 ; fine dots, zones 

 5 and 6A; unmarked, zone 6B and deferent duct. 

 (After B. L. Reid and K. W. Cleland, Australian J. 

 Zool., 5, 223-246, 1957.) 



periodic acid-Schiff (PAS) reaction, are 

 also reduced in the rat by castration (Ma- 

 neely, 1958). All such responses can be cor- 

 rected entirely or in part by the administra- 

 tion of testosterone propionate in adequate 

 doses (Cavazos, 1958, and others). Maraud 

 and Stoll ( 1958) have presented evidence to 

 show, in the chicken at least, that epi- 

 didymal morphogenesis from the undiffer- 

 entiated Wolffian duct is dependent on a 

 factor, presumably androgen, elaborated by 

 the primitive testis; in the absence of the 

 gonad, the epididymis remains in an undif- 

 ferentiated state. The rat epididymis also 

 seems to depend on testicular androgen for 

 its early neonatal differentiation (Cieslak, 

 1944). Posterior hypothalamectomy of the 

 male guinea pig is followed by extensive de- 

 generation of the reproductive organs, in- 

 cluding the epididymis (Soulairac and Sou- 

 lairac, 1959) ; subsequent administration of 

 chorionic gonadotrophin (25 I.U.) and tes- 

 tosterone propionate (2.5 mg.) results in 

 only a slight recovery of the epididymal epi- 

 thelium at sacrifice 8 days after injection. 



