TUNICA VAGINALIS. 241 



sections are made of the hardened organ, it will be 

 found that the intertubular spaces are occupied by 

 the blue substance, and, since they are proved by 

 the injection to be in free communication with the 

 lymphatics which leave the organ, the spaces are 

 to be looked upon as giving origin to the lymphatics. 



Preparation 13. Isolation of the seminife- 

 rous tubules. For obtaining the tubules isolated 

 for a considerable length, pieces of the testis (pre- 

 ferably human) are placed for a day or two in 

 hydrochloric acid, diluted with -J its volume of 

 water, and maintained at 30 C. They are then 

 allowed to lie in water until the tubules can be 

 readily separated with needles (Mihalkovics, Lud- 

 wig's "Arbeiten," 1874). Teased-out preparations 

 of the fresh testis-substance are also to be made in 

 serum, to exhibit the form, stages of development, 

 and movements of the spermatozoa. For the object 

 last named the preparation should be examined on 

 the warm stage. 



Preparation 14. Epithelioid cells of semi- 

 niferous tubules. To exhibit the fact that the 

 apparently structureless basement membrane of the 

 seminiferous tubules is in reality composed of layers 

 of flattened epithelioid cells, a portion of the testi- 

 cular substance is partially unravelled in distilled 

 water, and some of the tubules which are thus 

 isolated are dipped into nitrate of silver solution 

 for a minute, and, after being again rinsed in water, 

 are mounted in glycerine and exposed to the light ; 

 the lines of junction between the flattened cells are 

 by this means made evident. 



Preparations 15, 16. Tunica vaginalis. The 

 tunica vaginalis is to be prepared in the same way 

 as the other serous membranes (with nitrate of 

 silver), partly unbrushed to show the epithelioid 

 covering, and partly brushed tor the sake of exhibit- 

 ing the parts beneath. For the preparation of the 

 visceral part, the process is similar to that adopted 

 for the pericardium covering the surface of the heart 

 21 



