574 GENITAL ORGANS OF THE STALLION 



part of the spermatic cord, and is very tortuous near the testicle; on reaching the 

 attached border of the gland it passes backward in a fiexuous manner, giving 

 branches to the testicle and epididymis, turns around the posterior extremity, and 

 runs forward on the free border to the anterior extremity. It is partially embedded 

 in the tunica albuginea, and detaches lateral branches which ascend and descend in 

 a tortuous fashion on each surface of the testicle; these give off small laranches 

 which enter the gland on the trabeculae and septa. The veins on leaving the 

 testicle, form a network, the pampiniform plexus, around the arterj^ in the sper- 

 matic cord. The spermatic vein, which issues from this plexus, usually joins the 

 posterior vena cava on the right side, the left renal vein on the left side. The 

 lymph-vessels follow in general the course of the veins and enter the lumbar lymph 

 glands. The nerves, derived from the renal and posterior mesenteric plexuses, 

 form the spermatic plexus around the vessels, to which they are chiefly distributed. 



THE SCROTUM 



The scrotum, in which the testicles and the adjacent parts of the spermatic 

 cords are situated, is somewhat globular in form, but is commonly asymmetrical, 

 since one testicle — more often the left — is the larger and more dependent. It 

 varies in form and appearance in the same subject, according to the condition of its 

 subcutaneous musculaj tissue. The latter contracts on exposure to cold, so that 

 the scrotum is drawn up and becomes thicker and wrinided; when relaxed under the 

 influence of heat or fatigue, or from debility, it becomes smooth and pendulous, 

 with a constriction or neck superiorly. It consists of layers which correspond 

 with those of the abdominal wall; considered from without inward, these are: 



(1) The skin, which is thin, elastic, usually dark or black in color, and smooth 

 and oily to the touch. It presents scattered short fine hairs, and is abundantly 

 supplied with very large sebaceous and sweat glands. It is marked centrally by a 

 longitudinal raphe scroti ; this is continued forward on the prepuce and behind on 

 the perineum. 



(2) The dartos (Tunica dartos) is reddish in color and is closely adherent to 

 the skin except superiorly. It consists of fibro-elastic tissue and unstriped muscle. 

 Along the raphe it forms a median partition, the septum, scroti, which divides the 

 scrotum into two pouches. Dorsally the septum divides into two layers which 

 diverge on either side of the penis to join the abdominal tunic. At the bottom 

 of the scrotum fibers connect the dartos closely with the tunica vaginalis (and thus 

 indirectly with the tail of the epididymis), constituting the scrotal Ugament.^ 

 Elsewhere the dartos is loosely connected with the underlying tunic by areolar 

 tissue which contains no fat. 



(3) The scrotal fascia, which is apparently derived from the oblique abdom- 

 inal muscles. 



It has been customary to describe three layers of fascia, in conformity with the accounts 

 given in text-books of human anatomy. These are: (1) The intercolumnar or spermatic fascia, 

 derived from the margin of the external inguinal ring; (2) the cremasteric fascia, derived from the 

 internal obhque muscle; (3) the infundibuliform fascia, derived from the fascia transversahs. 

 The first two cannot be distinguished by dissection and the third is (in the scrotum) fused with 

 the parietal peritoneum of the timica vaginahs. 



(4) The parietal layer of the tunica vaginalis. — This is a fibro-serous sac which 

 is continuous with the parietal peritoneum of the abdomen at the internal inguinal 

 ring. It is thin above, but is thick in its scrotal part, where iti is strengthened by 

 fibrous tissue (Lamina fibrosa) derived from the transversalis fascia. It will be 

 described further under the caption tunica vaginalis. ^ 



1 This is a remnant of the gubemaculum testis of the foetus. 



2 The tunica vaginahs is not a part of the scrotum in the strict or narrow sense of that term, 

 but is included here on practical grounds. 



