INJECTING BLOOD-VESSELS AND GLAND-TUBES. gi 



for the carmine mass of Ranvier. Take 125 cc. of the blue solution 

 and heat it on a water-bath, and when the gelatine is fluid and 

 still on the water-bath, add the warm blue solution in a small 

 quantity at a time and stir briskly. The glass rod should show no 

 granules on it when it is withdrawn from the mass. Filter the 

 mass through new flannel. Even the best gelatine gives a precipitate 

 at first, but it disappears with heat. 



Other injection masses are used, e.g., a watery solution of 

 Briicke's blue, or gelatine and silver nitrate. These are referred 

 to in the text. 



Brass Syringe. Many good injections have been made with a 

 brass syringe. ' The syringe should have a long barrel, and be 

 warmed by repeatedly sucking up hot water before the injecting 

 fluid is drawn into it. When the injection mass is forced into 

 the blood-vessel, the pressure should be applied steadily, and should 

 not be so great as to rupture the small blood-vessels. 



When the blood-vessels of an animal are to be injected, deeply 

 narcotise an animal with chloroform, e.g., a rabbit or a rat ; make 

 a vertical incision through the skin from the lower part of the 

 neck to the ensiform cartilage, cut through the sternal cartilages, 

 turn up the breast-bone, and pull the sides of the thorax apart 

 to reveal the contents of the chest. Open the pericardium and 

 make a snip into the right ventricle. Tie a ligature round the 

 upper part of the sternum to prevent escape of the injection 

 through divided vessels. Wash the blood out of the chest. Snip 

 off the apex of the heart, whereby the cavity of the left ventricle 

 is opened into. 



Insert a cannula into the left ventricle and push its nozzle into 

 the aorta. Tie it firmly into the aorta with a stout thread. 

 Place the animal in a bath in warm water at 40 C. If "a syringe 

 is to be used, by means of a pipette fill the cannula with the 

 injecting mass, and attach the syringe and force the mass onwards 

 into the blood-vessels. This is done by slow, steady pressure. 

 It takes fifteen or twenty minutes to make a good injection. 

 Any sudden increase of pressure is apt to cause rupture of blood- 

 vessels and consequent extravasation of the injection mass. We can 

 judge when a part is well injected by the colour of semi-trans- 

 parent parts, such as the gums or the skin. They must be deeply 

 coloured by the injection mass if the injection is successful. 



Continuous Air Pressure. Most frequently injections are now 

 made by continuous air pressure. The apparatus used should consist 

 of a tin trough sufficiently large to contain the animal to be injected, 

 and contain sufficient water to cover it. The water is kept at 

 40 C. by moans of a gas-burner or spirit-lamp. In the same trough 

 are placed the injection masses in Wolffs bottles. Each Wolff's 



