THE KIDNEY. l8/ 



across transversely and hardened in alcohol. Thin sec- 

 tions are made across the entire organ, including cortex, 

 medulla, and papilla, stained double and mounted in 

 balsam. 



Isolated Tubules. A small fragment of fresh kidney, 

 including both cortical and medullary portions, is placed 

 in a mixture of equal parts of alcohol and strong hydro- 

 chloric acid ; the acid partially dissolves the intertubular 

 tissue, so that after a time the tubules can easily be pulled 

 apart. This is usually effected in about twelve hours ; 

 but the specimen should be examined from time to time 

 after it has been in the acid for eight hours, and removed 

 as soon as the object is accomplished. It is allowed to 

 soak for a few hours in water to remove the acid, and 

 then small bits are torn off, including cortical and medul- 

 lary substance, and the tubules carefully separated on a 

 slide. They are extremely brittle, and great care must 

 be used in their isolation ; this may be done by needles, 

 or better, by allowing small drops of water to fall upon 

 the specimen on a slide, from a pipette. When the dis- 

 sociation is partially effected, the excess of water should 

 be removed with filter paper, and a mixture of equal 

 parts of saturated solution of picric acid and glycerin 

 added, in which it is mounted and preserved. 



Sections of Uninjected Human Kidney. A perfectly 

 fresh human kidney is cut into small pieces and hardened 

 in strong alcohol. Sections are made in a plane vertical 

 to the surface of the organ, including both cortical and 

 medullary portions, and also parallel to the surface, 

 through the cortex. They are stained double and 

 mounted in glycerin. 





