TECHNIC. 343 



having a specific gravity of 1.12 (for this purpose kidney tissue is used 

 taken from an animal killed twenty-four hours previously). It is then 

 washed, teased, and examined in glycerin (Schweiger-Seidel). Fuming 

 nitric acid (40%), applied for a few hours to small pieces of tissue, occa- 

 sionally isolates the uriniferous tubules very extensively. The further 

 treatment is then the same as after hydrochloric acid. A 35% potassium 

 hydrate solution may also be employed. The isolated pieces are, however, 

 not easily preserved permanently. 



The epithelium of the uriniferous tubules may be isolated either in 

 YI alcohol or, according to R. Heidenhain (83), in a 5^ aqueous solu- 

 tion of neutral ammonium chromate. The latter method shows clearly 

 the striation of the epithelium. 



The autophysiologic injection with indigo-carmin, applied as in the 

 case of the liver, fills the uriniferous tubules, which may then be further 

 examined in sections. 



The blood-vessels are examined in injected specimens (injection 

 of the kidney is easily accomplished). In larger animals the injection is 

 made into the renal artery, while in smaller ones the whole posterior half 

 of the body is injected through the abdominal aorta. 



The ureter and bladder are cut open, fixed, and then sectioned. 

 In this way the organs are shown in a collapsed condition, in which the 

 arrangement of the epithelium is totally different from that found in the 

 distended organs. In order to observe them in the latter condition the fix- 

 ing agent is injected into the ureter or bladder, when, after proper liga- 

 tion, they are placed in the same fixing agent. 



The usual fixing fluids are employed in the demonstration of the 

 suprarenal capsule; but mixtures containing chromic acid, whether 

 Flemming's fluid, chromic acid, or its salts, are of special importance in 

 the examination of the organ, since the medullary substance of the supra- 

 renal capsule stains a specific brown when treated by these mixtures (a con- 

 dition only reduplicated in certain cells of the hypophysis). This brown 

 staining also occurs when the cortical and medullary portions are entirely 

 separated, as is the case in certain animals and during the development 

 of the suprarenal capsule. The fat found in the cells of the suprarenal 

 cortex is not identical with that of the rest of the body, as it may be dis- 

 solved by chloroform and oil of bergamot out of tissue fixed with osmic 

 acid (Hans Rabl). 



