oe 
1893.] | Microscopy. 583 
appearance, the subject is still open. Their conclusions may be quite 
correct, but examination from external appearance does not prove it. 
One great trouble arising in the discussion of this subject is that the 
destruction of the object consequent upon analysis and thin section 
prevents a satisfactory and competent determination. 
MICROSCOPY. 
A Method for Injecting the Blood-Vessels in Birds.— 
I presume all who give a laboratory course in Comparative Anatomy 
have, in common with myself, experienced difficulty in injecting the 
arterial and venous systems of birds. The usual directions are to 
inject the arterial system through the pectoral artery, and the venous 
system either through the pectoral vein or through the coecygeo-mesen- 
teric vein. The blood of birds coagulates very rapidly, and even when 
the procedure is carried out as expeditiously as possible, failure fre- 
quently occurs from the inability of the operator to remove the greater 
part of the blood from the animal, or from vexatious delays in tying 
a canula in the divided vessel. For some time I have been using the 
following method, and have not failed in securing the most satisfactory 
results. It possesses the additional advantage of being quickly per- 
formed. 
The bird, a pigeon for example, is placed under a bell-jar and chloro- 
formed in the usual way. While the bird is getting under the influence 
of the anesthetic, the operator should see that there is, within conven- 
ient reach, a scalpel, a pair of stout scissors with both points rounded 
off, two canulae and the necessary ligatures for tying them in place. 
As soon as the pigeon is thoroughly under the anesthetic, the bell- 
jar is removed, a towel is wrapped about the head and a few drops of 
chloroform poured over it; the feathers are rapidly plucked from the 
breast and abdomen to a point just anterior to the cloaca; the skin is 
divided the entire distance over the keel, and the pectoral muscles dis- 
sected off from their attachment to the keel and body of the sternum 
for a distance of half an inch on either side of the keel. 
The muscles attached to the posterior margin of the sternum are 
next divided elose to the sternum for the distance of half an inch on 
either side of the median line; now raise the sternum carefully and 
divide the attachment of the heart. Beginning at the outer angle of 
the divided abdominal muscles, the body of the sternum is cut through 
ìThis department is edited by C. O. Whitman, University of Chicago. 
