TESTES. 



807 



forming an incomplete vertical septum, called the mediastinum testis (corpus 

 Highmorianum\ 



The mediastinum testis extends from the upper, nearly to the lower border 

 of the gland, and is wider above than below. From the front and sides of this 

 septum, numerous slender fibrous cords (trabeculse) are given off, which pass to 

 be attached to the inner surface of the tunica albuginea: they serve to maintain 

 the form of the testis, and join with similar cords given off from the inner sur- 

 face of the tunica albuginea, to form spaces which inclose the separate lobules 

 of the organ. The mediastinum supports the vessels and ducts of the testis in 

 their passage to and from the substance of the gland. 



The Tunica Vasculosa (pia mater testis), is the vascular layer of the testis, 

 consisting of a plexus of bloodvessels, held together by a delicate areolar tissue. 

 It covers the inner surface of the tunica albuginea, sending off numerous pro- 

 cesses between the lobules, which are supported by the fibrous prolongations 

 from the mediastinum testis. 



Structure. The glandular structure of the testis consists of numerous lobules 

 (lobuli testis). Their number, in a single testis, is estimated by Berres at 250, 

 and by Krause at 400. They differ in size according to their position, those in 

 the middle of the gland being larger and longer. The lobules are conical in 

 shape, the base being directed towards the circumference of the organ, the apex 

 towards the mediastinum. Each lobule is contained in one of the intervals 

 between the fibrous cords and vascular processes, which extend between the 

 mediastinum testis and the tunica albuginea, and consists of from one to three, 

 or more, minute convoluted tubes, the tubuli seminiferi. The tubes may be 

 separately unravelled, by careful dissection under water, and may be seen to 

 commence either by free caecal ends, or by anastomotic loops. The total num- 

 ber of tubes is considered by Monro to be about 300, and the length of each 

 about sixteen feet: by Lauth, their number is estimated at 840, and their 

 average length two feet and a quarter. Their diameter varies from 2 J c th to 

 ygflth of an inch. The tubuli are pale in color in 

 early life, but, in old age, they acquire a deep yellow 

 tinge, from containing much fatty matter. They 

 consist of a basement membrane, lined by epithe- 

 lium, consisting of nucleated granular corpuscles, 

 and are inclosed in a delicate plexus of capillary 

 vessels. In the apices of the lobules, the tubuli 

 become less convoluted, assume a nearly straight 

 course, and unite together to form from twenty 

 to thirty larger ducts, of about ^th of an inch in 

 diameter, and these, from their straight course, 

 are called vasa recta. 



The vasa recta enter the fibrous tissue of the 

 mediastinum, and pass upwards and backwards, 

 forming, in their ascent, a close network of anas- 

 tomosing tubes, with exceedingly thin parietes; 

 this constitutes the rete testis. At the upper end 

 of the mediastinum, the vessels of the rete testis 

 terminate in from twelve to fifteen or twenty 

 ducts, the vasa efferentia: they perforate the tunica 

 albuginea, and carry the seminal fluid from the 

 testis to the epididymis. Their course is at first 

 straight; they then become enlarged, exceedingly 

 convoluted, and form a series of conical masses, 

 the coni vasculosi, which, together, constitute the 

 globus major of the epididymis. Each cone con- 

 sists of a single convoluted duct, from six to eight inches in length, the dia- 

 meter of which gradually decreases from the testis to the epididymis. Op- 



Fig. 439. Vertical Section of 

 the Testicle, to show the arrange- 

 ment of the Ducts. 



Tuni 



