TESTIS 



333 



crystalloids, the significance of which is unknown. The nature of the 

 granules is discussed by Whitehead (Amer. Journ. Anat., 1912, vol. 14 

 pp. 63-71). 



The interstitial cells, although not intimately related with the vessels, 

 are thought to produce an internal secretion, and certain observations 

 suggest that the sexual instinct is dependent on these cells rather than 

 upon the spermatozoa (cj. Whitehead, Anat. Rec., 1908, vol. 2, pp. 177- 

 182). During senile atrophy of the testis, the interstitial cells at first 

 increase; later they are destroyed. At the same time the basement mem- 

 brane becomes thickened and hyaline, fat droplets accumulate, and the 

 sexual cells disappear from the tubules, leaving the sustentacular cells. 



The arteries of the testis are branches of the internal spermatic artery, 

 which descends through the spermatic cord, beside the ductus deferens. 

 The branches enter the testis in part through the mediastinum, and in 



Interstitial cells. 



Connective tissue 



FIG. 331. FROM A CROSS SECTION OF THE TESTIS OF A MAN TWENTY-TWO YEARS OLD. X 50. 



part through the tunica vasculosa. They extend through the septula, 

 and form capillary plexuses around the convoluted tubules. The veins 

 accompany the arteries. Lymphatic vessels are numerous in the tunica 

 albuginea and extend among the tubules. Nerves from the spermatic 

 plexus surround the blood vessels; the presence of intraepithelial endings 

 has not been established with certainty. 



Convoluted Tubules. The shape of the tubules of the testis has been 

 repeatedly investigated, but whether blind ends occur has not been 

 established; generally the tubules end in loops. Anastomoses have been 

 recorded, not only between the tubules in a single lobule* but also between 

 adjacent lobules. The extent of the anastomoses among the closely 

 coiled tubules is difficult to determine. 



For more than seventy years eminent anatomists have recorded their success or 

 failure in finding blind ends Krause, Kolliker, Sappey and LaValette St. George 

 state that they exist; Hyrtl, Henle, Mihalkovics and Eberth fail to find them. Two 



