1026 THE MALE REPRODUCTIVE ORGANS 



bottom of the scrotum. It begins to descend in the early i)art of the third month 

 of foetal life, reaching the internal inguinal ring in the sixth month. It then passes 

 obli(iUely through the structures of the abdominal wall, preceded by a pouch of 

 peritoneum and ])ushing l)efore it, in succession, the subperitoneal tissue, an 

 infundibuliform prolongation of the fascia transversalis, a few libers of the internal 

 ol)lique (whieh form i)art of the external cremaster), and the intercohmmar fascia, 

 which braces togetlier the pillars of the external inguinal ring. At the eighth 

 month it appears at the external ring, and reaches the l)ottom of the scrotum shortly 

 before birth. 



The cause of this migration is still uncertain. The theory usually adoi)ted is 

 that the descent is effected partly by the development of the pelvic and lumbar 

 regions which grow upwards, and in a manner leave the testicle, fixed by the guber- 

 naculum, Ijehind. This accounts for the change of position to the level of the 

 inguinal canal, but the mechanism of the further descent into the scrotum is 

 unknown. It was formerly attributed to the progressive shortening of the gulier- 

 naculum, and in accordance with this view, the unstriped muscular fibres connect- 

 ing the bottom of the gland with the scrotum are regarded as the remains t)f the 

 central and principal gubernacular band, while the lateral bands, ceasing to act after 

 the testicle has reached the external ring, are drawn down into the scrotum and 

 appear as scattered groups of fibres, the internal cremaster of Henle, lying around 

 the elements of the spermatic cord (fig. (526). 



In certain individuals, the descent of one or both testicles into the scrotum is 

 intercepted, and cryptorchism results. This condition is normal in certain 

 animals (elephants, cetacea, etc.), but in man is always associated with defective 

 evolution of the organ, and consequent suppression of function. 



The peritoneal sac carried with the testicle is at first continuous with the 

 al)dominal peritoneum. In most cases the tul^e of communication gradually 

 narrows, and at length, within a few days after birth, becomes entirely closed. 

 Sometimes, however, the process of obliteration is more or less incomplete. 

 Should it fail altogether, a portion of the abdominal viscera may pass into the 

 tunica vaginalis, and constitute the congenital variety of inguinal hernia ; or 

 peritoneal fluid may accumulate in the testicular sac and form a congenital 

 hydrocele. IVIore frequently the continuity of the tunica vaginalis with the 

 peritoneum is interrupted; but a slender pouch of peritoneum, the processus 

 vaginalis, may run into the inguinal canal, and even through the external ring 

 into the cord, or the tunica vaginalis may be prolonged upwards uiH:»n the cord for 

 a considerable distance. 



Should any portion of the abdominal contents enter the processus vaginalis, it 

 may pass through the inguinal canal as a hernia, and descend into the scrotum. 

 If at the same time the upward extension of the tunica vaginalis be present, the 

 hernia with its sac may pass within it or invaginate it, and a surgeon called upon 

 to operate in such a case would pro!)ably open the tunica vaginalis before reaching 

 the peritoneal sac, and thus meet with three layers of serous memltrane before 

 exposing the extruded intestine. A hernia of this kind is called ' infantile.' Cystic 

 tumors may !)e formed by the distension of small unoliliterated segments of the 

 funicular portion of the tube, and are called encysted hydroceles of the cord. 



Structure (fig. 623). — The testicle proper consists of a tul)ular parenchyma 

 enclosed witliin a strong fil)rous tunic, the tunica albuginea. 



The tunica albuginea (figs. 621, 623) is a dense, white, inelastic capsule of 

 about one-twenty-fifth of an inch (1 mm.) in thickness in the greater part of its 

 extent, but reaching two or three times this admeasurement beneath the epididymis 

 where it forms the mediastinum testis, or Corpus Highmorianum, It is 

 perforated at its upper and 1)ack part by the eft'erent seminal tul»es which go to 

 form the globus major of the epididymis, and from its inner surface })ass a number 

 of sustentacular processes, in the form of thread-like fibro-museular filaments and 

 delicate septal planes of connective tissue, the trabeculae. The mediastinum 

 extends forwards from the upper half of the posterior border, o('cu])ying al)out a 

 fourth of the sagittal and a third of the transverse diameter of the interior, and is 

 tunnelled by lilood-vessels and a network of seminal tubes (the rete testis). The 

 trabeculae radiate from the deep aspect of the mediastinum to the inner surface 



