REPRODUCTION. 887 



and opens into it by numerous small ducts situated about the openings of the 

 vasa deferentia. Its function is to contribute prostatic fluid to the semen. The 

 composition of this fluid has been already mentioned (p. 885) ; its specific use 

 is not known. 



Cowper's Glands. Cowper's glands (Fig. 306, C.g), two in number, are 

 tubulo-racemose glands, the ducts of which open into the spongy portion of 

 the urethra by two orifices situated some two inches below the openings of the 

 vasa deferentia. Their viscid secretion is thought to be one of the components 

 of the seminal fluid, but its specific function is unknown. It has been sug- 

 gested that Cowper's fluid cleanses the urethra of urine and of semen, instead 

 of contributing actually to the seminal fluid. 



The Penis. The penis (Fig. 306, pn) has as its constant function merely 

 the conveying of the urine to the outside world, and for this purpose it has no 

 special features beyond those belonging to the urethra, which runs throughout 

 its whole length. Specifically, however, it is the intromittent organ, and 

 serves to convey the semen into the genital passages of the female. This 

 function is based upon its power of erection, and this power is dependent 

 upon the presence of the erectile tissue which constitutes the bulk of the 

 organ. The erectile tissue is arranged in the form of three long cylindrical 

 masses imperfectly separated from, but parallel to, one another and extending 

 lengthwise. Of these, the two corpora cavernosa lie at the sides, and meet each 

 other in the middle line along the upper side of the penis ; the corpus spongi- 

 osum lies in the middle line below, and is pierced throughout its length by the 

 urethra. At its proximal end each corpus is enlarged into a bulbous part, 

 and is covered by a layer of muscular fibres constituting a distinct muscle the 

 bulbs of the corpora cavernosa by the ischio-cavernosi (erectores penis), that of 

 the corpus spongiosum (called bulbus urethrce) by the bulbo-cavernosus (accel- 

 erator urince). At its distal end each corpus cavernosum terminates bluntly, 

 while the corpus spongiosum projects farther and enlarges to form the extrem- 

 ity of the organ, the glans penis. Each corpus is spongy in consistence, being 

 formed of a trabecular framework of white and elastic connective tissue and 

 plain muscular fibres, with cavernous venous spaces, and is covered by a tough 

 fibrous tunic. When the spaces are distended with blood the whole organ 

 becomes hard, rigid, and erect in position. The mechanism of erection will 

 be studied more in detail later (p. 901). The penis, especially toward its ter- 

 mination, is beset with end-bulbs, Pacinian bodies, and other nerve-termina- 

 tions, that make it particularly sensitive to external stimulation. 



0. THE FEMALE REPEODUCTIVE ORGANS. 



The female reproductive organs, already mentioned, have as their specific 

 functions the production of the essential female germ-cells, the ova, their trans- 

 ference to the uterus, and, if unfertilized, to the outside world ; if fertilized, 

 the protection and nutrition of the developing embryo, its ultimate transfer- 

 ence to the outside world, and the nutrition of the child during early in- 

 fancy. 



