MALE GENITAL ORGANS OF THE DOG 593 



The prepuce has a narrow orifice, around which there are stiff hairs. The 

 cavity is very long, and is partially divided by a circular fold into a posterior narrow 

 part and a much ^^dder anterior part. The lining membrane of the posterior part is 

 papillated, and is in close contact with the penis; it contains numerous lymph 

 nodules, the largest of which occur in the fundus. In the dorsal wall of the wide 

 part there is a circular opening which leads into a cul-de-sac, the preputial diver- 

 ticulum. This pouch is ovoid in form (when distended), and varies greatly in size 

 in different subjects. It extends for the most part backward over the narrow part 

 of the prepuce. Its cavity is partially divided by a narrow septum. It contains 

 usually decomposing urine and macerated epithelium, which have a characteristic 

 and very unpleasant odor. Concrements have been found in it. 



Oehmke found that a cast of the pouch in a Yorkshire boar weighing about 500 pounds 

 measured 9 cm. in length, 12}/^ cm. in breadth, and 6 cm. in height. The opening into the pre- 

 puce will admit two fingers in the adult, but is ordinarily closed by folds of the lining membrane. 

 The sac is much smaller m animals which were castrated young, and the opening is vertical and 

 further back ; in them it is often empty or contains only a little clear urine. The pouch is gland- 

 less, but contains many small lymph nodules; it is covered by a layer of striped muscle which is 

 mainly derived from the homologue of the protractor of the prepuce of ruminants. 



The urethra has a very long pelvic part (ca. 15 to 20 cm. long in the adult) ; 

 it is covered (with the pars disseminata of the prostate) by a thick urethral muscle, 

 except dorsally, where there is a dense fibrous layer. Surrounding the mucous 

 membrane there is a rich venous plexus, which is regarded as a stratum cavernosum. 

 Outside of this the pars disseminata of the prostate is easily distinguished on cross- 

 section by its yellow color. The prostatic ducts are numerous and small. The 

 ductus deferentes and the excretory ducts of the vesiculse seminales have sht-Iike 

 openings close together in small diverticula on either side of the colliculus seminalis. 

 The latter has the form of a round prominence. A small uterus masculinus may 

 occur in the colhculus between the ducts, but it is often absent. There is a distinct 

 bulb at the root of the penis. It has a dense covering, which in part resembles 

 fibro-cartilage. The erectile tissue here is highly developed. The cavernous 

 spaces are large, and the trabeculae contain much unstriped muscle; between the 

 spaces there are numerous arteries. The penile part is of small caliber, and is 

 surrounded by erectile tissue which, however, does not extend to the extremity of 

 the penis. 



MALE GENITAL ORGANS OF THE DOG 



The scrotum is situated about half way between the inguinal region and the 

 anus. The skin covering it is pigmented and is covered sparsely with fine hairs. 

 The raphe is not very distinct. 



The testicles are relatively small, and have a round-oval form. The long 

 axis is oblique, and is directed upward and backward. The mediastinum testis 

 is central and is well developed. The epididymis is large, and is closely attached 

 along the dorsal part of the lateral surface of the testicle. 



The spermatic cord and the tunica vaginaUs are long; they cross the side of 

 the penis very obliquely. The upper end of the tunic is sometimes closed, so that 

 there is then no vaginal ring. The ductus deferentes have narrow ampullffi. 



The vesiculse seminales are absent. 



The prostate is relatively large; it is yellowish in color, dense in structure, 

 and lies at or near the anterior border of the pubis. It is globular, and surrounds 

 the neck of the bladder and the urethra at their junction. A median furrow mdi- 

 cates a division into two lateral lobes. The capsule and stroma contam a large 

 amount of unstriped muscle. The ducts are numerous. Lobules of prostatic 

 38 



