234 MANUAL OF HISTOLOGY. 



are connected by transverse ones, and thus depressions are 

 formed. 



The muscular coat consists of smooth muscular fibres ar- 

 ranged in three layers : an inner, or longitudinal, which is 

 feebly developed ; a middle, or circular, which is substantial in 

 character, and an external or longitudinal. This coat is less 

 developed in young children than in adults. 



In the external fibrous coat, or tunica adventitia of the vas 

 deferens, are found bundles of smooth muscular fibres running 

 longitudinally. They are derived from the cremaster interims, 

 which muscle is well developed at the origin of the vas deferens, 

 but gradually diminishes in size as it enters the abdominal cavity. 



The vas deferens possesses a dense plexus of medullated 

 nerve-fibres,- the spermatic plexus, situated in the tunica ad- 

 ventitia. From this plexus several smaller trunks proceed 

 which penetrate into the muscular and mucous coats. Scat- 

 tered along these nerve-trunks are seen small ganglion-cells, 

 which are round or oval. 



The blood-vessels of the testicle come from the internal 

 spermatic artery and enter the gland partly at the corpus 

 Ilighmori and partly upon its surface. They surround the 

 seminiferous tubules as a capillary plexus of large meshes. 

 The epididymis receives its blood from the deferential artery, 

 and also to some extent from the vessels of the testicle. The 

 tas deferens possesses a rich capillary network in its muscular 

 coat and also in its mucous membrane beneath the epithelium. 



The nerves of the testicle come from the internal spermatic 

 plexus ; their mode of termination has not as yet been satis- 

 factorily explained. Letzerich, however, describes fine nerve- 

 fibres in the testicles of mammals ; they penetrate the connec- 

 tive tissue and membrana propria, terminating between this 

 layer and the first row of cells in dark granular masses. 



The lymphatic system of the testicle consists of a series of 

 lacuna, lined with endothelial cells, which surround the semi- 

 niferous tubules; in the interstitial connective-tissue, these 

 communicate with canals from which others are given off to 

 the connective-tissue septa of the lobules. Beneath the tunica 

 albuginea another network of lymphatic canals is also found, 

 which penetrate the tunic, especially upon the dorsum of the 

 organ, and finally, uniting with the lymphatics of the epididy- 



