XXII.] STEUCTURE OF THE KIDNEY. 235 



9. Cut vertical sections of a rabbit's or dog's bladder 

 which has been distended with and hardened in 

 ammonium bichromate 2 p.c Observe 



a. The thin external fibrous coat. 



b. The muscular coat consisting of an outer 

 generally speaking longitudinal layer and an 

 inner generally speaking circular layer; inside 

 this may also be seen a third layer with fibres 

 running in various directions chiefly longi- 

 tudinally. 



c. The sub-mucous coat of connective tissue. 



d. The mucous coat of 



a. Connective tissue rather finer but con- 

 tinuous with that of the sub-mucous 

 coat. 



^. Epithelium consisting of an inner layer 

 (next to the cavity of the bladder) of a 

 single row of roughly cubical cells, a 

 median layer of a single row of pear- 

 shaped cells, and an outer layer (next 

 the basement membrane) of two or 

 three rows of elongated cells between 

 and beneath the processes of the pear- 

 shaped cells. 



The form of the cells naturally varies with 

 the degree of distension of the bladder. 



10. Cut transverse sections of a rabbit's or dog's 

 ureter which has distended and hardened like 

 the bladder (§ 9). 



