XXV] KIDNEY 199 



layers of cells, broadly speaking increasing in size from 

 without inwards. The form of the cells naturally varies 

 with the degree of distension of the bladder. 



DEMONSTRATIONS. 



1. Radial section of kidney (dog) injected from 

 the ureter. Note the divisions of the outflow and 

 collecting tubes. 



2. Nitrate of silver preparation of mammalian 

 kidney to show the outlines of the cells of the tubes. 

 Note especially the irregular outlines of the cells of 

 the convoluted tubes. 



3. Transverse section of kidney of frog; (osmic 

 acid). Note the granules of the cells, and the inner 

 clear or striated border. 



4. Transverse sections of ureter (potassium bichro- 

 mate 2 p.c.; hsematoxylin) (a) taken near the kidney, 

 (b) taken near the bladder. Note the epithelium 

 similar in general to that of the bladder; the rather 

 thick coat of connective tissue beneath the epithelium ; 

 the unstriated muscular coat consists of inner longi- 

 tudinal and outer circular fibres; the outer fibrous 

 coat ; in (b), the longitudinal muscle bundles outside 

 the circular muscle. 



NOTES. 



Isolation of kidney tubes. A. small radical piece of fresh 

 kidney of a guinea-pig or rat is placed in a mixture of 1 part 

 hydrochloric acid and 2 parts water for 4 hours to a day ; it 

 is washed well with water, strips torn off; and the tubes 



