1288 THE URO-GENITAL SYSTEM. 



where the globus major is attached, inferiorly where the cauda epididymidis is in 

 contact, and posteriorly where the blood-vessels and nerves enter the organ from 

 the funiculus spermaticus or spermatic cord. 



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 im- 

 perfectly divide the organ into a number of wedge-shaped parts called lobuli testis 

 (Fig. 1005). All the septa end posteriorly in a mass of fibrous tissue which is 

 Tunica albuginea directly continuous with the tunica al- 



septuia testis s" W-^ buginea, and which projects forwards into 



Lobuli ^ e testis along its posterior border. This 

 structure receives the name of mediastinum 

 testis, or corpus Highmori, and is traversed 

 by an exceedingly complicated 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 lymph vessels 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 

 Medium S ym ' s *&>*** network of vessels (tunica vasculosa) 



is formed on the deep surface of the tunica 

 FIG. 1005. TRANSVERSE SECTION OF THE ,, , ,, r . -, ,, 



TESTIS AND EPIDIDYMIS. albuginea and on the sides 01 the septa. 



The mediastinum, the septa, and the 



tunica albuginea form a framework enclosing a number of imperfectly isolated 

 spaces which are filled by a loosely packed substance of a light brown colour 

 called the parenchyma testis. 



The parenchyma is composed of enormous numbers of much-convoluted semini- 

 ferous tubules, called tubuli seminiferi contort!, and completely fills up the intervals 

 between the septa. The minute tubules look like fine threads to the unaided eye, 

 and are but loosely held together by a small amount of connective tissue. Usually 

 three or four tubules are found in each lobule of the gland, and the total number 

 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 number of slender tubes which run a straight 

 course. These latter are called tubuli seminiferi recti, and open into a complicated 

 network of fine canals situated in the substance of the mediastinum, called the rete 

 testis. The tubules are much more twisted and convoluted in the cortical part of] 

 the gland, near the tunica vaginalis, than in the region of the mediastinum, and ' 

 often give off side branches which, according to some observers, may effect 

 anastomoses between, the tubules. It appears doubtful, however, if the semini-j 

 ferous tubules of the testis do really anastomose. 



Microscopic sections show that the walls of the seminiferous tubules are composed oi| 

 a basement membrane and of an epithelial lining, formed of several layers of cells,. 

 Certain cells of this epithelium are, in the adult, constantly undergoing transformation j 

 into spermatozoa, and the appearance of the tubules in section varies much, according tc 

 age and to the greater or less activity of the epithelial cells. 



The secretion of the seminiferous tubules is carried through the tubul: 

 seminiferi recti into the rete testis, and leaves the latter, to reach the canal o 

 the epididymis, through from fifteen to twenty minute tubules called ductul: 

 efferentes testis or efferent ductules. These latter pierce the tunica albuginea anc 

 enter the caput epididymidis where it is in direct contact with the superio: 

 extremity of the testis. Each efferent ductule is at first straight, but soor' 

 becomes much convoluted, and forms a little conical mass of twisted tubule, callec 



