282 PRACTICAL HISTOLOGY [XXXV 



The rete testis, without special basement membrane, 

 and lined by much flattened epithelium. 



The efferent tubules and canal of the epididymis. 

 Note the fibrous and unstriated muscle coats, both thin ; 

 the epithelium consisting of columnar ciliated cells, 

 with some small cells near the basement membrane. 



In the canal of the epididymis the cells are long and slender, 

 but there is some variation in different animals ; in the efferent 

 tubules and in the coni vasculosi the cells are shorter and 

 broader. 



To see the masses of spermatozoa in the tubes, a section of 

 the epididymis of the rat treated as the testis in 9 should be 

 made. 



9. Section of testis of rat (mercuric chloride, stain 

 deeply in bulk with hsematoxylin, cut in paraffin). 

 Note the slight amount of connective tissue and the 

 absence of interstitial cells. 



The epithelium varies in arrangement in different 

 tubes. Observe the following forms. 



a. An outer single layer of small cells, lining cells 

 with deeply stained nuclei ; next to this a single layer 

 of larger cells, the nuclei being in some stage of division, 

 most probably in the tangle stage, the spermatogenic 

 cells ; a layer consisting of four or five small cells, 

 spermatoblasts, with less stained nuclei ; lastly sper- 

 matozoa, the deeply stained heads of some lying close 

 to and between the outermost layer of the spermato- 

 blasts. 



b. The lining cells are of two kinds, neither staining 

 deeply ; one kind, the supporting cells, have a flattened 

 base, they narrow on the inner side, and from them pass 

 bands of faint lines to the lumen, thus dividing the 



