572 GENITAL ORGANS OF THE STALLION 
Structure of the Testicle and Epididymis.—The greater part of the surface 
of the testicle is covered by a serous membrane, the tunica vaginalis propria, which 
is the visceral layer of the serous envelop of the cord and testicle; this is reflected 
from the attached border of the gland, leaving an uncovered area at which the 
vessels and nerves in the spermatic cord reach the testicle.! Beneath this serous 
covering is the tunica albuginea, a strong capsule composed of dense white fibrous 
tissue and unstriped muscle-fibers. When the tunic is cut, the gland substance, 
which is soft and reddish gray in color, protrudes. From the attached border and 
from the deep face of the tunica albuginea trabecule and septa of connective tissue 
Fic, 513.—InGuinat ReGion oF STALLION, WITH TesTICLES EXPoseD. 
a,a’, Testicles; b, scrotum, opened and reflected; c, tunica vaginalis communis, opened and reflected; d, reflection 
of tunica vaginalis enclosing scrotal ligament; e, tunica vaginalis propria (mesorchium); /, ductus deferens; g, 9’, tail 
of epididymis; 4, body of same; 7, head of same; k, sinus epididymidis; 1, spermatic vessels showing through tunica 
vaginalis propria; m, spermatic artery; n, prepuce; n’, raphé; 0, preputial orifice. (After Ellenberger-Baum, Top. 
Anat. d. Pferdes.) 
and unstriped muscle (Septula testis) pass into the gland and subdivide the 
parenchyma, into lobules (Lobuli testis). The larger trabeculse radiate from the 
attached border into the central part of the gland. 
A distinct mediastinum testis, such as is present in man and many animals, does not exist in 
the horse. The trabeculz and interlobular septa form a network which shows no special conden- 
sation in any part of the gland. In correlation with this is the absence of a rete testis, formed by 
the anastomosis of the seminiferous tubules in the mediastinum. 
The spaces imperfectly marked off by the septa contain the parenchyma 
testis, which consists of seminiferous tubules (Tubuli seminiferi), supported 
1Tn the normal state the surface of the testicle is quite smooth on account of the serous 
covering. Frequently, and especially in old subjects, local inflammation has produced roughen- 
ing of the surface and thread-like proliferations. 
