346 ANATOMY OF THE DOMESTIC FOWL 



needle or in the tubing. A small cannula should be used, since 

 the endothelial lining of the arteries are easily injured and diflS- 

 culty may thus be created. 



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 length- 

 wise of the artery being careful not to strip back the endothelial 

 lining of the artery. Allow as much of the blood as wiU 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 coagu- 

 lates 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'f rom 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 aU blood possible drained from the arteries. 

 After the injection is completed the bird may be plucked and im- 

 mersed 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. — Longitudmal 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 lacimae, the canaUcuU, and the 

 Haversian system. 



