Kidney. 87 



take one and divide it transversely into several pieces 

 and place them in the fluid. The other may be divided 

 longitudinally by one cut, and large kidneys may be 

 hardened in chromic acid in this way. Sections 

 may be cut by the freezing microtome, and are best 

 stained in logwood, or double stained in carmine and 

 indigo- carmine (page 37). To show the minute struc- 

 ture of the cells in the collecting tubes, fine striation of 

 epithelium, &c., Heidenhain's method is the best. 



Cut the kidney into small pieces longitudinally in the 

 direction of the pyramids, and place them in a 5 per 

 cent, solution of chromate of ammonia, from 24 48 

 hours in a stoppered bottle, then wash for several hours 

 until no more color comes away, changing the water 

 several times, and place in dilute and then in strong 

 spirit in the ordinary way (page 13). 



Sections should be made both vertical and transverse 

 of the cervical and medullary portion of the kidney, as 

 well as large sections longitudinal and transverse of the 

 whole organ ; by this mean ' the general structure of 

 the organ and the arrangement of the tubes can be 

 examined, while in the smaller sections, some of which 

 should be mounted under thin covers, the minute struc- 

 ture can be studied ; for this no stain succeeds so well 

 as logwood. 



Examine sections of the cortical part for the striation 

 of the epithelial cells, and notice the imbrication in 



some parts. 



BLADDER URE TER . 



Cut into small pieces and harden in chromic acid 

 mixture. 



