266 THE AMERICAN MONTHLY [Sept. 



common salt, 1 to 200. Soak in absolute alcohol, and 

 make transverse sections. 



Injection of the Ureter. — This operation, even more 

 difficult than the preceding, can be performed on the 

 dog. Remove the kidney from a recently killed animal, 

 taking care to preserve the end of the ureter, and inject 

 the Prussian blue mass without gelatine, tying the can- 

 ula in the ureter. Pressure should be very slight. . . . 

 Put the organ in bichromate, harden in gum and alco- 

 hol. There are often a fevs^ points in the kidney which 

 are properly injected. 



The Ureter; Dissociation of Epithelial Cells. — Open a 

 segment of ureter and macerate it for 24 hours in the i 

 alcohol ; scrape the internal surface with a scalpel, and 

 spread the result in a drop of the I alcohol. Stain by 

 picro-carmine, mount in glycerine. 



Sections. — Make longitudinal and transverse sections 

 of the organ fixed by alcohol, and hardened in gum and 

 alcohol ; stain in picro-carmine. 



The Bladder. — In the frog tie the open- 



ning of the cloaca with a strong string, open the ab- 

 domen and seek the terminal end of the large intestine. 

 Gently inject the tube. The liquid collects in the cloaca 

 and is forced into the bladder. When that organ is 

 properly distended, tie the large intestine, detach the 

 posterior members of the frog with the bladder and the 

 intestine, and place the whole in a large quantity of the 

 liquid used to make the injection 



Inject with the I alcohol; in 24 hours scrape the inner 

 surface with the scalpel, spread the result on a slide in 

 a drop of the I alcohol. Stain in picro-carmine, mount in 

 glycerine. [Isolated Epithelial Cells.) 



Muscles. — The preceding bladder from which the 

 epithelium has been carefully brushed, should be spread 

 on a slide, inner surface upward. Stain by hsematoxy- 

 lin and eosine : mount in balsam. 



