VARIES. 237 



the tunica albuginea, which passes over into the deeper-lying 

 venous cortical network. This is connected in turn with the 

 large central venous spaces of the erectile bodies. In the 

 second case the arteries pass directly over into the veins, 

 opening into the deep venous cortical network or directly into 

 the cavernous venous spaces. 



The efferent veins (venae, emissaries) collect partly from the 

 deep cortical network, partly from the central cavernous 

 spaces. The veins from the interior of the corpora cavernosa 

 pass through the meshes of the cortical network. This 

 arrangement is of great importance in the process of erection. 

 When the cortical network is well filled, the venae emissariae 

 are compressed, so that the exit of the blood cannot keep pace 

 with its entry. This condition is increased by the direct con- 

 nection of some of the arteries with the cavernous spaces. The 

 veins pass through the tunica albuginea and join to form the 

 vena dorsalis and the venae profundae penis. 



In the corpus cavernosum urethrae (c. spongiosum), which 

 is surrounded also by a thin tunica albuginea, we may distin- 

 guish two regions. The deep region is formed by a rich 

 development of venous networks in the submucosa urethrae. 

 The peripheral part is composed of erectile tissue which is like 

 that of the corpora cavernosa, except for the fact that its meshes 

 are smaller and the connective-tissue strands more delicate. 

 The arteries here never open directly into the venous spaces, 

 but always break up into capillaries before reaching the veins. 



The glans penis consists of much-branched and convoluted 

 veins, which are held together by an abundance of firm con- 

 nective tissue. 



The tunica albuginea of the cavernous bodies and the glans 

 penis are supplied richly with nerves (see Nerve-endings). 



2. FEMALE SEXUAL ORGANS. 



A. The Ovaries. 



The ovaries are alveolar glands possessing no ducts. Their 

 product the egg cell is secreted in a special way, to be 



