TESTIS. 



117 



recta, which in the corpus Highmori form the rete testis. These tubes are much thinner than 

 the seminal tubes, and there is a constriction where the one tube passes into the other. They 

 are lined by a single layer of low, columnar cells. They lead into the wider coni vasatlosi and 

 the epididymis (p. 1 17). (Indicate the capsule and sections of the tubules in PI. XXVIII., Fig. i.) 



(H). Study the tubuli seminiferi, especially in a transverse section. Observe the thick 

 membrana propria ; within it are the seminal cells, arranged in several layers. The outer 

 seminal cells, next the membrana propria, consist of a single layer of transparent, polyhedral, 

 nucleated, and faintly-defined cells. Internal to these are several layers of cells the inner 

 seminal cells. They are polyhedral, nucleated, somewhat granular cells, though they are 

 usually more spherical in shape next the lumen of the tube. 



Study the innermost cells : some of them may be found with their nucleus partially 

 divided, or even divided into two daughter nuclei, and then the whole cell divides, so as to 

 give origin to two daughter cells. These cells undergo further changes, and give origin to 

 the spermatozoa, and are hence called spermatoblasts. These cells, after certain intermediate 

 changes in their nuclei and cell-contents, split up into a group of young spermatozoa, which 

 are arranged in fan-shaped groups, the head or nucleus of each spermatozoon being directed 

 towards the membrana propria of the tube. This development of the spermatozoa in groups 

 is quite characteristic, and several groups may be seen in a single tube ; afterwards they 

 become detached to constitute spermatozoa. They are best seen in dammar preparations. It 

 is to be remembered that all these stages are not found in a section of any one tube, but 

 several tubes must be examined to see all the stages. (Indicate tlie cells lining a tubule and 

 the developing spermatozoa in PI. XXVIIL, Fig. 2.) 



THE EPIDIDYMIS AND VAS DEFERENS. 



PREPARATION. Exactly the same as directed for the testis. It is convenient to use the 

 epididymis of a sheep. Make transverse sections, stain them in logwood, and mount them in 

 dammar, and do the same with the vas deferens. 



Transverse Section of the Epididymis. EXAMINATION (L and H). We traced the seminal 

 tubules until they formed the rete testis. This system of tubes opens into ten or twenty vasa 

 efferentia, which form the coni vasculosi, which again open into the canal of the epididymis, and 

 this again into the vas deferens. Sections of the vasa efferentia and the convoluted tube 

 of the epididymis are well seen, the latter being much larger than the former. Each transverse 

 section of the epididymis shows tubes with a relatively large lumen, lined with columnar 

 epithelium, which rests on a membrana propria, supported by non-striped muscle. The 

 epithelium is columnar and ciliated, and the cilia are relatively long. (Indicate the general 

 arrangement in PI. XXVIIL, Fig. 3, and the ciliated epithelium in Fig. 4.) 



At the bases of these cells branched pigment-cells are found, especially in the testis of the 

 sheep. Notice the normal amount of interstitial connective tissue, in which nerves and blood- 

 vessels may be recognised. 



The vas deferens has a mucous, a muscular, and an outer coat, or adventitia. The epithe- 

 lium of this canal is columnar, and carries cilia only in that part next the epididymis. 



The blood-vessels of the testis are studied in the ordinary way. 



