Obtaining Plasma from Birds *

The usual method of obtaining large quantities of plasma from fowl is to bleed the animals from the carotid artery under ether anesthesia. When it is considered that these animals have small heads but huge lower extremities, the advantages of using the ischiadic artery' become apparent at once. To obtain an accurate comparison of the sizes of the vessels, segments of the carotids and of the ischiadics at the usual sites of insertion of the canulas were embedded in paraffin and sectioned. By projectoscopy and planimetry were determined the cross-sectional areas of the lumen, of the zone bounded by the outer border of the muscularis, and of that bounded by the outer layer of adventitia. From these, the diameters of the areas were calculated, assuming them to be perfect circles. The results obtained from the vessels of three animals were averaged. The average diameter of the lumen of the ischiadic was thus found to be exactly three times as great as that of the carotid, the muscular wall was 2.8 times as thick, and the outside diameters of the vessels were in the ratio of I to 3 in favor of the carotid. The ischiadic artery is superficially situated, a long segment can easily be exposed, and the head of the animal is left free for the convenient induction of anesthesia. By this method even young birds can easily be bled with a large yield. For example, in one operation, a rooster approximately 7 months old and 6.5 lbs. in weight yielded 140 cc. of blood from which 71.5 cc. of plasma were harvested. In another instance a 10-lb. bird yielded 195 cc. of blood from which 93.5 cc. of plasma were obtained, and in a third the yield of plasma was 96.5 cc. from 188 cc. of whole blood. This rooster weighed 9.5 lbs.