THE BABBIT. 121 



ventricle into the aorta, tighten the ligature, and knot it 

 firmly. 



If an injecting-syringe be not at hand, use as a cannula 

 a glass tube so drawn out as to have a notch in it that it 

 may be firmly tied ; slip on the outer end of this a short 

 piece of rubber tubing, and insert into this the nozzle of 

 an ordinary syringe. 



For the injection mass, fill an ordinary tumbler half full 

 of fine plaster of Paris, colored with a little carmine or 

 yellow ochre ; fill the tumbler with water, stir well, and 

 immediately strain the liquid through coarse muslin into a 

 second tumbler. Fill the syringe and inject immediately, 

 as the plaster soon sets. Give a steady, even pressure. 

 On removing the syringe, the rubber tube should be 

 plugged to prevent escape of the liquid. 



If the specimen be not injected, the veins can usually be 

 distinguished from the arteries by their greater diameter, 

 thinner walls, and by being of a darker color, retaining 

 the blood, while the arteries are usually empty or nearly 

 so. 



OKGANS OF THE ABDOMINAL CAVITY. 



1. Slit the skin in the middle line from the breastbone 

 to the pelvis, and strip it well back to the sides. 

 Observe the thin abdominal muscles, which form 

 the ventral wall of the abdomen. Carefully slit the 

 abdominal wall in the middle line from the pelvis to 

 the breastbone ; from the middle of this slit cut out- 

 ward on each side and turn back the flaps. 



2. The lining of the abdomen is the peritoneum; what 

 does it tell the sense of touch ? 



3. Observe the coiled intestine, noting any variations in 



