594 MALE GENITAL ORGANS OF THE DOG 
tissue (pars disseminata) are also found in the wall of the urethra for a short distance 
further back. The gland is subject to much variation in size, and is often enlarged, 
especially in old subjects. 
The position of the prostate varies. When the bladder is empty and contracted, the gland 
is entirely in the pelvic cavity and may be an inch or more behind the anterior border of the 
pubis. When the bladder is full, the prostate is often largely or entirely prepubic. 
The uterus masculinus is a small compressed saccule in the colliculus seminalis. 
The bulbo-urethral glands are absent." 
The penis presents several special features. In its posterior part there are two 
distinct corpora cavernosa, separated by a median septum penis. In its anterior 
part there is a bone, the os penis, which in large dogs reaches a length of four inches 
(ca. 10 cm.) or more. It is regarded as a part of the corpus cavernosum which has 
Fig. 528.—ExTernat GENITAL ORGANS OF MALE Dog; VEeNTRO- Fic. 529.—InNTERNAL GENITAL ORGANS OF 
LATERAL VIEW OF PREPARATION. Mate Doa; Dorsat View. 
1, Serotum; 7¢’, tunica vaginalis; 2, epididymis; 8, vascular 1, Urinary bladder; 2, ureter; 3, ductus 
deferens; 4, prostate; 5, urethral muscle; 6, 
part of spermatic cord; 4, ductus deferens; 5, prepuce; 6, pars longa 
bulb of urethra; a, abdominal wall; 6, ilium; 
glandis; 6’, corpus cavernosum penis; 7, bulbus glandis; 7’, con- 
tour of bulbus in erection; 8, ischio-cavernosus muscle; a, acetab- c, ischium. (After Ellenberger, in Leisering's 
ulum; 6, obturator foramen. (After Ellenberger, in Leisering’s Atlas.) 
Atlas.) 
ossified. Ventrally it is grooved for the urethra; dorsally it is convex, and an- 
teriorly it becomes smaller and has a curved fibrous prolongation.? The glans 
penis is very long, extending over the entire length of the os penis; its anterior 
part, the pars longa glandis, is cylindrical, with a pointed free end; behind this 
there is a rounded enlargement, the bulbus glandis. Both are composed of erectile 
tissue. The two dorsal veins arise from the bulbus glandis, pass backward on the 
dorsum penis, and unite at the ischial arch. A small muscle (M. compressor ven 
dorsalis penis) arises from the tuber ischii on either side; the two converge on the 
dorsum penis near the bulbus glandis. They compress the dorsal veins, and may 
also tend to elevate the penis and thus assist in copulation, The other muscles 
offer no features worthy of special description. 
1They are present in the cat, and are the size of a pea. 
2In the young subject it has a prolongation composed of hyaline cartilage, which becomes 
fibrous later. 
