ORGANS OF THE BODY. 



Fig. 546. From the testis of a calf. 1. Transverse 

 section of a seminiferous tubule, a, b, walls of the 

 latter; <-, capillary network; d, connective-tissue 

 framework; e, lymphatic canals. 2. Side view of 

 the wall of a seminiferous tube ; a and ft, wall 



They then gradually combine to form one single wide canal (g, y) 

 0-3767-0*45 mm. in diameter; which turns and twists upon itself still 

 further in forming an elongated body known as the corpus and cauda 

 epididymis. 



By degrees this tube, of which the epididymis is composed, becomes less 

 tortuous and of greater calibre, its diameter amounting on an average to 

 2 mm. It is now known as the vas deferens (h). Frequently before 

 this it receives the addition of a short coecal branch, the vas aberrans of 

 Haller (i). 



Turning now to the structure of the seminal gland, we find in the first 

 place that it presents a sustentacular substance. This is found in the 

 form of fibres of connective- 

 tissue (fig. 546, 1, d), radiat- - ' ^^ 

 ing from both septa and capsule 

 throughout the whole organ. In 

 this connective-tissue numerous 

 cells and nuclei are encountered 

 in young animals : its bands vary 

 in thickness ; in the calf from 

 0-0564 to 0-0113 mm. 



These bundles of connective- 

 tissue (Mihalcowicz) are enve- 

 loped in those flat membraneous 

 cells of which we have already 

 spoken ( 130, 223), and to which we shall again have occasion to refer 

 in considering the arachnoid. These cells cover like a membrane both 

 seminal tubules and blood-vessels, leaving, however, chinks between them, 

 which serve a purpose in the lymphatic circulation. 



In the human and mammalian testicle besides a number of peculiar cellu- 

 lar elements, undergoing pig- 

 mentary and fatty metamor- 

 phosis, the " interstitial 

 cells," are met with, at 

 times in great abundance. 

 They are usually arranged 

 in bands, their diameter be- 

 ing in the cat 0-014-0-020 

 mm. They may envelope 

 the vessels like a sheath. 



The interstices of this sus- 

 tentacular substance are 

 occupied by the seminiferous 

 tubules (figs'. 545, 546, 1 a; 

 547, a, b) whose diameter 

 is on an average from 

 0-1 128 to 0-1421 mm. By the aid of the microscope we learn that the mem- 

 brana propria is represented by a coat (sharply defined from the interstitial 

 connective-tissue) of tough texture, and fibrous or banded structure, contain- 

 ing elongated nuclei (fig. 545, a; 546, 1 a, b, 2 a, b). Its thickness ranges 

 from 0-0046 to 0'048 mm. In man this wall is particularly well marked. 



It consists, according to Mihalcowicz, of several layers of flattened cells 

 united with one another in the form of a membrane. The most internal 

 layer is quite impervious ; but the external is open and net-like. 



Fig. 547. From the testis of the calf, a, seminiferous 

 tubules in profile ; b, in transverse section ; c, blood-vessels ; 

 ef, lymphatics. 



