THE TESTIS. 1105 
and overlapping, tou some extent, the posterior part of the outer surface of the testis. 
_ The upper, somewhat swollen part of the epididymis, is called the globus major 
(caput epididymidis), and overhangs the upper end of the testis, to which it is 
directly connected by numerous emerging ducts, by connective tissue, and by the 
serous covering of the organ. The lower and smaller end is termed piobis minor 
(cauda epididymidis), and is attached by loose areolar tissue and by the serous 
covering to the lower end of the testis. The intermediate part or body (corpus 
epididy midis) i is appled against, but is separated from, the teats part of the 
outer surface of the testis “by an involution of the serous covering of the organ, 
which forms an intervening pocket termed the digital fossa. 
Attached to the globus major, or to the adjoining part of the upper extremity of the 
testis, there are usually one or two minute pedunculated bodies, called hydatids of the 
epididymis or of the testis (appendices testis), which have a developmental interest. 
Above the globus major, and in front of the lower part of the spermatic cord, there is also 
sometimes a small body present, called the organ of Giraldes or paradidymis. ‘his is 
rarely seen in the adult. 
Tunica Vaginalis.—The cavity within which the testis and its epididymis 
are placed is lined by a smooth serous membrane—the tunica vaginalis—which 
resembles in appearance and structure the peritoneum from which it is originally 
derived. The cavity is considerably larger than the contained structures, and 
extends not only down to a lower level than the testis, but also reaches upwards to 
a higher level than the gland. The sac or cavity tapers as it is traced upwards, 
and above the level of the testis the spermatic cord bulges forwards into its 
posterior part. The tunica vaginalis not only lines the cavity for the testis, but is 
reflected from the posterior wall of the scrotal chamber over the testis and epididymis, 
giving a covering to each. The part of the membrane lining the cavity is called 
the parietal portion (lamina parietalis) of the tunica vaginalis, while the part 
clothing the testis and epididymis is the visceral portion (lamina _ visceralis). 
Between the outer surface of the testis and the body of the epididymis, the 
visceral part of the tunica vaginalis dips in and lines an interval called the digital 
fossa (sinus epididymidis). On the other hand, the tunica vaginalis is absent where 
the globus major and globus minor of the epididymis are adherent to the testis, 
and similarly the serous covering is incomplete posteriorly, where the various 
structures forming the spermatic “cord enter or leave the testis and epididymis. 
From the lower part of the testis or epididymis a small crescentic fold of the tunica 
vaginalis passes downwards to the bottom of the sae. 
“Structure of the Testis and Epididymis.— Beneath the serous tunica vaginalis 
the testis is invested by an external coat, composed of dense white inelastic 
fibrous tissue called the tunica albuginea, from the deep surface of which a number 
of slender fibrous bands or septa dip into the gland. These—the septula testis— 
imperfectly divide the organ into a number of parts called lobes or lobules (lobuli 
testis, Fig. 751). All the septa end posteriorly in a mass of fibrous tissue which is 
directly continuous with the tunica albuginea, and which projects forwards into 
the testis along its posterior border. This structure receives the name of mediastinum 
testis, or corpus Highmori. The mediastinum is traversed by an exceedingly com- 
plicated network of fine canals, into which the minute tubules which compose the 
substance proper of the testis open. The mediastinum is also pierced by the 
arteries, veins, and lymphatics of the testis. These vessels enter the posterior 
border of the organ, and traversing the mediastinum, spread out on the fibrous septa 
which radiate towards all parts of the deep surface of the tunica albuginea. In 
this way a delicate network of vessels (tunica vasculosa) is formed on the deep 
surface of the tunica albuginea and on the sides of the septa. 
The testis is composed. of enormous numbers of much convoluted seminiferous 
tubules (tubuli seminiferi contort), which fill up the intervals between the septa. 
These minute tubules look like fine threads to the unaided eye, and are but 
loosely connected together. Usually but three or four are found in each lobule of 
the gland, and the ‘total number of tubules in the testis has been estimated at 
about 600. The seminiferous tubules, after a course of about two feet in length, 
pass towards the mediastinum testis, and unite, at acute angles, to form a smaller 
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