584 The American Naturalist. [June, 
with the stout, blunt-pointed scissors, in a direction forward and 
inward, until a point is reached directly over the origin of the vascular 
trunks; repeat on the opposite side. Now grasping the keel firmly 
with the left hand, make traction directly upward, at the same time 
steadying the bird with the right hand; by this procedure the sternum 
is broken equally across, and the heart exposed without causing any 
damage to it or to the vascular trunks. Next, tear the pericardium | 
open as quickly as possible, seize the heart, still strongly beating, 
between the thumb and index finger of the left hand, invert the bird 
over a sink and cut off with the blunt-pointed scissors the apex of the 
heart. In this way the blood-vessels are thoroughly emptied and the 
bird killed without any unnecessary suffering. 
Although the description of the procedure may make it seem long, 
I have repeatedly done it in less than three minutes. i 
canula is now inserted through the left ventricle into the aorta, 
and a ligature placed around it close to the point where the aorta 
leaves the heart. In passing the ligature around the canula, care 
should be exercised not to injure the vena cava or the right auricle. A 
second canula is passed through the right ventricle into the right 
auricle and secured by tying a stout ligature about the whole heart. 
Ihave found that the best injecting mass is Gage’s modification of 
Pausch’s, colored with vermilion or ultramarine blue ; this does not 
pass through the capillaries, sets quickly, leaving the vessels well-dis- 
tended with a firm mass. 
I employ a constant pressure apparatus in injecting, using a pressure 
of 100 mm. for the artery, but only 60 mm. for the vein; more than 
this will usually cause a rupture. 
W. S. MILLER. 
Univ. of Wisconsin. 
