Ink Perfusion for Displaying Capillaries in the Chicken

Abstract

A chicken was anesthetized with Na-phenobarbital, 130 mg/kg, and the external ischiatic artery was exposed. Heparin, 90 units/kg, was injected into the brachial vein, after which a cannula was inserted into the exposed ischiatic artery. Heat was applied to the head to produce vasodilation. Perfusion through the cannula was made at about 150 mm Hg pressure and consisted of 30 ml of a biological type of Pelikan ink to which was added NaNO₂ to make a 0.02% solution. After the bird was killed by an overdose of anesthetic, the skin around the perimeter of the femoral feather tract was cauterized, the tract removed, attached to a stainless steel wire net, fixed for 1 hr in 10% formic acid, then dehydrated in 4 changes of acetone, 1 hr each, followed by a 5th change for 12 hr. The dehydrated specimens were placed in methyl benzoate, the 1st change for 1 hr and the 2nd until clear (3-15 hr). This procedure exhibits small vessels and capillary networks within the integument, but if only the vessels larger than capillaries are to be studied, they can be shown by slowly injecting 15-30 ml of the perfusion mixture into a peripheral vein. The still beating heart will distribute the ink to other regions of the body, thus allowing the vessels to be traced in excised tissue.