PENIS 349 



communicate with one another. Each is surrounded by a very dense 

 albuginea, i mm. thick, divisible into an outer longitudinal and an inner 

 circular layer of fibrous tissue. The septum is formed by the median 

 fusion of these layers. The cavernous or erectile tissue of which these 

 corpora are composed is essentially like 

 that around the urethra. 



All three cavernous bodies are sur- 

 rounded by fascia and subcutaneous 

 tissue containing blood vessels, lym- 

 phatics and nerves. The lymphatic 

 vessels form a superficial and a deep 

 set, the latter receiving branches from 

 the urethra. The principal sensory 

 nerves are the medullated dorsal nerves 



of the penis. They terminate in many -_ r -- g 



tactile corpuscles in the papillae beneath FIR. 351. CROSS SECTION OF A PENIS. 



the Skin, in bulboUS and genital COrpUS- 



i . ,1 j ,. ,. i nosa penis; f., urethra; g., corpus caver- 



cles in the deeper connective tissue, and nosum urethras. 



in lamellar corpuscles found near or in 



the cavernous bodies. Free endings also occur. The sympathetic nerves 

 are from a continuation of the prostatic 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 AND GENERAL FEATURES. 



Although it is probable that sex is determined at the time of the fer- 

 tilization of the ovum, and that it cannot be modified by subsequent con- 

 ditions of any sort, the sex of young embryos cannot be recognized. All 

 human embryos of 13 mm. possess a prominent genital papilla; they have 

 both Wolffian and Miillerian ducts, in so far as the latter have developed; 

 and they contain genital ridges which are still in an "indifferent stage" 

 it cannot be said whether they will become ovaries or testes (cj. Fig. 

 326, p. 328). In the female the Miillerian ducts become highly developed, 

 the Wolffian ducts degenerate, and the genital ridges produce ovaries. 



The Miillerian Ducts. Before reaching the urogenital sinus, the lower 

 ends of the Miillerian ducts are in contact, being situated between the 

 Wolffian ducts (Fig. 352). The figure here reproduced represents a por- 



