648 



THE HUMAN BODY. 



The Male Reproductive Organs. The testes in man are 

 paired tubular glands, which lie in a pouch of skin called the 

 scrotum. This pouch is subdivided internally by a partition 

 into right and left chambers, in each of which a testicle lies. 

 The chambers are lined inside by a serous membrane, the 

 tunica vaginalis, and this doubles back (like the pleura round 

 the lung) and covers the exterior of the gland. Between the 

 external and reflected layers of the tunica vaginalis is a space 

 containing a small quantity of lymph. 



The testicles develop in the abdominal cavity, and only 

 later (though commonly before birth) descend into the scrotum, 

 passing through apertures in the muscles, etc. , of the abdom- 

 inal wall, and then sliding down over the front of the pubes, 

 beneath the skin. 'The cavity of the tunica vaginalis at first 

 is a mere offshoot of the peritoneal cavity, and its serous mem- 

 brane is originally a part of the peritoneum. In the early years 

 of life the passage along which the testis passes usually becomefe 

 nearly closed up, and the communication between the peri- 

 toneal cavity and that of the tunica vaginalis is also obliterated. 

 Traces of this passage can, however, readily be observed in 

 male infants; if the skin inside the thigh be tickled a muscle 

 lying beneath the skin of the scrotum is 

 made to contract reflexly, and the testis 

 is jerked up some way towards the 

 abdomen and quite out of the scrotum. 

 Sometimes \he passage remains per- 

 manently opeii and a cpil of intestine 

 may descend along it and enter the 

 scrotum, constituting an inguinal 

 hernia or rupture. A hydrocele is an 

 excessive accumulation of liquid in the 

 serous cavity of the tunica vaginalis. 



Beneath its covering of serous mem- 

 brane each testis has a proper fibrous 

 tunic of its own. This forms a thick 

 mass on the posterior side of the gland, 

 from which partitions or septa (i, Fig. 

 185) radiate, subdividing the gland 

 into many chambers. In each chamber 

 lie several greatly coiled seminiferous tubules, a, a, averaging in 

 length 0.68 metre (27 inches) and in diameter only 0.14 mm. 

 ( T ^_ inch) . Their total number in each gh nd is about 800. 



FIG. 185. Diagram of a 

 Vertical section through the 

 testis. a, a, tubuli semini- 

 feri; b, vasa recta: d, vasa 

 efferentia endii^g in the 

 coni vasculosi; e, e, epidi- 

 dyiriis. &, vas deferens. 



