314 THE AMERICAN MONTHLY [Oct., 



Microscopical Technique Applied to Histology. — VH. 



[FROM THE FRENCH OF RENE BONEVAL.] 

 (Continued from page 270.) 



Carmine mass. — This furnishes beautiful injections, 

 but the difficulty in exactly neutralizing it without pre- 

 cipitating the carmine makes the Prussian blue prefera- 

 ble for every day work. . . . 



Liquid masses. — In certain circumstances it is advan- 

 tageous to use a cold liquid mass. The saturated solu- 

 tion of Prussian blue acts well ; a solution of silver 

 nitrate (1 to 300) may be used to impregnate the endo- 

 thelium of the vessels. 



INJECTING. 



We advise beginning with the frog. 



Injecting with the blue gelatine. — Having immobilised 

 a large frog by piercing the medulla oblongata, cut the 

 sternum on a level with the xiphoid appendage, making 

 the incision parallel with the long axis of the body ; open 

 the pericardium, lift the heart out of the thorax and cut 

 off the point with scissors. Put the frog in warm water 

 (40°C) and wait for the blood to run out. Fill the syringe 

 (which has been warmed in a water-bath), with the in- 

 jection mass, put on a small canula and force out the air 

 by pushing in the piston while the syringe is held up- 

 right. The frog being now almost bloodless, introduce 

 the canula into the heart up to the aortic bulb and place 

 a ligature around the latter to hold the canula in posi- 

 tion. Make the injection gently. When the vessels are 

 full (it will then be difficult to push the piston), place a 

 ligature beyond the canula. . . . Put the frog in a large 

 vessel of two per cent of ammonia bichromate solution. 

 In a few hours, the gelatine being hard, open the abdo- 

 men to allow the liquid to penetrate more rapidly. Cut 

 sections after hardening in alcohol and imbedding in 

 gum. The preparation should be mounted in dammar. 



