Select for arterial dissection an old cock, as in a bird of this kind the arteries are larger and the difficulties are reduced. Select for bleeding and injection the ischiadic artery in the thigh region. With the sharp point of the thin blade of a knife make an incision lengthwise of the artery being careful not to strip back the endothelial lining of the artery. Allow as much of the blood as will escape before injecting; in fact, the arteries should be thoroughly emptied, so that there is no longer danger of a clot’s plugging some vessel and thus preventing its filling. Since the blood of most birds coagulates in about thirty seconds, this work must be done rapidly, care being exercised to keep the flow running as long as possible. After bleeding is completed, insert the cannula and tie the vessel tightly around the cannula to prevent the escape of the injecting fluid. See that all connections are sufficiently tight to prevent the escape of liquid under pressure. After the injection is completed, remove the cannula and tie the artery with a small twine, preferably cotton. Quickly remove all injecting fluid from the needle, the tubing, and the injecting chamber. During the operation of bleeding the cock may be chloroformed, care being taken not to administer chloroform to kill him; for it is necessary to maintain life as long as possible so that the heart may be kept beating and all blood possible drained from the arteries. After the injection is completed the bird may be plucked and immersed in the preservative fluid in the same manner as in the preparation for dissection for muscles. The arteries, the veins, and the nerves may now be dissected and studied in relation to one another and in relation to the muscles, the bones, and other structures. The skin should not be removed from the shanks till it is desired to dissect these parts, as the tissues quickly dry out. In fact, the tendons of the shanks and toes can best be dissected while the specimen is fresh. =A Study of the Structure of Bones.=—Longitudinal and transverse sections of old bone may be made by making thin longitudinal and transverse sections with the bone saw, and then by making them very thin with a fine three-cornered file. Examining under the low power microscope, we note the lacunæ, the canaliculi, and the Haversian system.