DUCTUS DEFERENS AND SEMINAL VESICLE 1257 



and some of whose tubules, becoming the efferent ducts, place the seminiferous tubules in com- 

 munication with the ductus deferens. The epididymis may therefore be said to be developed 

 from the mesonephros. The portions of this structure that are not concerned in the formation 

 of the efferent ducts disappear for the most part; a few of the tubules persist, however, as 

 rudimentary organs associated with the epididymis. Among these may be mentioned one or 

 more blindly ending, coiled tubules, varying from 5-30 cm. in length, which are connected with 

 the ductus epididymidis usually in the tail of the epididymis. They are known as the ductuli 

 aberrantes (fig. 1018) and may be regarded as persistent excretory mesonephric tubules. Another 

 of the rudimentary organs is the paradidymis {organ of Giraldes), which is a whitish body, 

 situated immediately above the head of the epididymis, and is composed of irregularly coiled 

 tubules, which terminate blindly at both extremities. They may be regarded as efferent 

 ducts that have failed to connect with the testis and are of interest in that they sometimes 

 develop into cysts connected with the epididj^mis. 



In addition there is frequently attached to the upper pole of the testis a sohd oval body 

 composed of connective tissue, known as the appendix testis {hydatid of Morgagni) (fig. 1017). 

 It measures from 3 to 8 mm. in length and its significance is doubtful. A similar, though 

 smaller structure, the appendix epididymidis, is attached less frequently to the head of the 

 epididymis. It is usually provided with a distinct stalk and contains a cavity; it is beheved to 

 represent the upper end of the Miillerian duct, present in the embryo and giving rise to the tuba 

 uterina in the female, but almost completely degenerating in the male. 



The testis begins its descent from the abdominal cavity into the scrotum at the third month 

 of fetal life and reaches the abdominal inguinal ring at about the sixth month, but it is not 

 until shortly before birth that it arrives at its final location in the scrotum. The cause of the 

 descent is still uncertain, but it is supposed to be partly due to the failure of a band of connective 

 tissue, which extends from the lower pole of the embryonic testis to the bottom of the scrotal 

 pouch, to keep pace with the growth of the body walls. This hgament, which is known as the 

 guhernaculum testis, thus becomes relatively shorter and draws the testis downward toward the 

 point of its attachment to the scrotum. There are various features in the descent, however, 

 that cannot be explained by the simple traction of the gubernaculum and it must be regarded 

 as a comphcated growth process whose meaning is yet uncertain. The gubernaculum testis 

 apparently undergoes degeneration after the testis has reached its definitive location and cannot 

 be recognized in connection with the adult testis. 



Occasionally the descent of the testis is interrupted, the organ remaining either in the 

 abdomen or in the inguinal canal. This condition of cryptorchism is always associated with a 

 suppression of the function of the organ. 



2. The Ductus Deferentes and Vesicul^ Seminales 



Each ductus deferens is the continuation of a ductus epididymidis and ex- 

 tends from the tail of the epididymis to the prostatic portion of the urethra. At 

 its beginning it ascends along the posterior border of the epididymis {testicular 

 portion) and is at first slender and tortuous (fig. 1018), but before reaching the 

 level of the head of the epididymis it becomes straighter and thicker (fig. 1017), 

 owing to the development in its walls of strong layers of longitudinal and circular 

 non-striated muscle tissue. Thence it is continued almost vertically upward as 

 one of the constituents of the spermatic cord {funicular portion) to the subcu- 

 taneous inguinal ring, and, entering this, traverses the inguinal canal {inguinal 

 portion), still forming a portion of the cord. At the abdominal ring it separates 

 from the other constituents of the cord and, looping over the inferior epigastric 

 artery near its origin, passes downward and backward over the lateral surface of 

 the bladder {pelvic portion). At the junction of the posterior and lateral surfaces 

 of the bladder it passes medially to the ureter and is then continued downward, 

 forward and medially upon the base of the bladder until it reaches the prostate 

 gland (fig. 1019), whose substance it traverses, as the ductus ejaculatorius, to open 

 into the prostatic portion of the urethra (see p. 1263). 



Just before it reaches the prostate gland each ductus deferens presents an 

 irregular spindle-shaped enlargement, the ampulla (figs. 1019, 1020), whose walls 

 are somewhat sacculated. Just beyond this it is joined upon its lateral surface 

 by a club-shaped lobulated structure, the vesicula seminalis (fig. 1019). Each 

 vesicle measures 4.5-5.5 cm. in length and has a greatest diameter of about 2 cm. 

 It rests upon the posterior surface of the bladder, lying parallel with and lateral 

 to the corresponding ductus deferens, and in its upper one-third is in relation 

 posteriorly with the peritoneum which forms the anterior wall of the recto- 

 vesical pouch, while below it is in contact with the anterior wall of the lower part 

 of the rectum, through which it may be palpated. Indeed, the two vesiculse, 

 together with the ductus deferentes, form the lateral boundaries of the triangular 

 area at the base of the bladder, throughout which that organ is in relation to the 

 rectum. 



