142 PRACTICAL ZOOLOGY. 



THE VALVES IN THE VEINS. 



Dissect back the skin from the throat of the rabbit, cat, 

 or dog, till the jugular veins are well exposed. Let the 

 head of the animal hang over the edge of the table ; note 

 that as the blood presses back toward the head it causes 

 marked bulging at certain points ; with the handle of the 

 forceps slightly sfrroke the vein toward the head, watching 

 the bulgings. Dissect out the jugular vein from the head 

 to the shoulder ; insert the nozzle of a syringe, first into 

 one end and then into the other, and show the effect of 

 forcing currents in each direction. Cut the vein open 

 along one side, pin inside out to a piece of a shingle and 

 examine the thin pockefr-like valves. Test the elasticity 

 of the vein. Note the smoothness of its inner coat. 

 Remove a piece of an artery and experiment in the same 

 way with it. 



DEMONSTRATION OP THE ACTION OE THE HEART. 



Get the heart and lungs entire. Dissect out the aorta 

 as before. Clear the pulmonary artery and cut off both 

 branches close to the lungs. Carefully trim away the 

 pericardium and clean the venae cavae inferior and supe- 

 rior. Turn the heart back and find one of the larger 

 pulmonary veins ; cut a hole in it near the lung and slip a 

 glass tube into it toward the heart ; this tube should have 

 a groove, made by drawing it out in the flame; tie the 

 tube firmly in, and ligature the other pulmonary veins 

 without stopping to trace them. Tie any and all connect- 

 ions with the heart now remaining and cut bej r ond the 

 ligatures. Get a retort-stand and two large glass funnels. 



