DEVELOPMENT OF THE FEMALE GENITAL ORGANS. 



principal sensory nerves are the medullated dorsal nerves of the penis. 

 They terminate in many tactile corpuscles in papillae of the skin, in bulb- 

 ous and genital corpuscles in the deeper connective tissue, and in lamel- 

 lar corpuscles found near or in the cavernous bodies. Free endings also 

 occur. The sympathetic nerves are from a continuation of the pros- 

 tatic plexus. They constitute the cavernous plexus, which includes the 

 major cavernous nerves accompanying the dorsal nerves of the penis and 

 the minor cavernous nerves which enter the roots of the corpora cavernosa 

 penis. The sympathetic nerves supply the numerous smooth muscles of 

 the trabeculae and cavernous blood vessels. They are said to be joined 

 by fibers from the lower spinal nerves, the nervi erigentes. 



FEMALE GENITAL ORGANS. 



DEVELOPMENT. 



During early embryonic development sex is indistinguishable and 

 perhaps undetermined. Since it is well known that the sex of mature 

 insects may be largely controlled by the amount of nutriment which the 

 larva receives, it has been thought that the sex of mammals may become 

 established in the course of their embryonic de- 

 velopment. All attempts to find the controlling 

 factors have failed and it is possible that the sex 

 is determined when the egg becomes fertilized. 



In both the male and female there are simi- 

 lar primitive sexual cells, genital ridges, Wolfiian 

 and Mullerian ducts, elongated urogenital sinuses 

 and prominent genital papillae. The structures 

 shown in Fig. 299, page 264, may belong with 

 either sex. The two Mullerian ducts reach the 

 allantois side by side, between the Wolrfian 

 ducts. They fuse with one another, beginning 

 at a short distance from their outlets and ex- 

 tending toward the allantois (Fig. 325, a detail 

 from Fig. 279, B, page 249). The fused portion 

 becomes divisible into the vagina below and the 

 uterus above; a thick layer of smooth muscle in 



the mesenchyma surrounding the Mullerian ducts characterizes the uterus 

 (Fig. 326). A fold of membrane, the hymen, which is found in the adult 

 at the orifice of the vagina, may mark the termination of the Mullerian 

 ducts. Some authorities, however, consider that more or less of the vagina 

 is an outpocketing of the urogenital sinus and that the hymen has no hing 



W.d. 



M.d. W.d. 



u.s. -/ 



FIG. 325. RECONSTRUCTION 

 SHOWING THE FUSION OF 

 THE MUELLERIAN DUCTS. 

 (After Keibel.) 



bl., Bladder; M.d., Mullerian 

 duct; u., ureter; ur., ure- 

 thra; U.S., urogenital 

 sinus; W.d., Wolffian 

 duct. 



