STRUCTURE OF THE TESTIS. 



p. 356 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 abdominal 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 membrane is originally a part of the perito- 

 neum. In the early years of life the passage along which 

 the testis passes usually becomes nearly closed up, and the 

 communication between the peritoneal 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 

 heneath 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 the passage 

 remains permanently open and a coil 

 of intestine may descend along it 

 and enter the scrotum, constituting 

 an inguinal hernia or rupture. A 

 liydrocele is an excessive accumula- 

 tion of liquid in the serous cavity of 

 the tunica vaginalis. 



Beneath its covering of serous 

 membrane 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. 160) radiate, subdivid- 

 ing the gland into many chambers. In each chamber lie 

 several greatly coiled seminiferous tubules, a, a, averaging 

 in length 0.68 meters (27 inches) and in diameter only 

 0.14 mm. (-J-JTJ- inch). Their total number in each gland is 



FIG. 160. Diagram of a 

 vertical section through the 

 testis. a, a, tubuli semini- 

 f eri ; 6, yasa recta ; d, vasa 

 efferentia ending in the 

 coni vasculosi; e, e, epidi- 

 dymis. /i,vas deferens. 



