INTRODUCTION. 7 



the tip so that they may be firmly tied into the artery or 

 vein. 



Most of the injections called for in the present work 

 can be made either through the aorta or through the ven- 

 tricle. The ventricle is cut open and the canula is forced 

 through this opening into the aorta, around which a string 

 is passed and tied, thus holding the tube firmly in place. 

 The syringe is then filled with the injecting fluid (see 

 below) and connected with the canula, when a pressure 

 upon the piston will force the fluid into the blood-vessels. 

 Too much pressure should not be exerted, as the vessels are 

 liable to rupture. It is advantageous in many cases to 

 first inject with 2 r 7 formol, which washes out the vessels 

 and helps to preserve the specimen. Then the colored 

 mass is employed. 



Various injecting fluids have been proposed, but the 

 following are ample for all purposes, and they have, be- 

 sides, the advantage of not requiring heat, which in the 

 case of some forms causes a softening of the walls of the 

 blood-vessels. 



Starch Injection Mass. Grind together in a mortar one 

 volume of dry starch, one of a 2%% aqueous solution of 

 chloral hydrate, and one-fourth volume each of 95% alcohol 

 and of the ' color.' The ' color' consists of equal volumes 

 of dry color (vermilion, chrome yellow, Prussian blue, etc.), 

 glycerine and alcohol. The mixture will keep indefinitely, 

 but requires thorough stirring before use and quick usage, 

 as the starch and color settle rapidly. 



Gum Injection Fluid. Make a rather thick (molasses- 

 like) solution of gum arabic in water ; color it with carmine 

 dissolved in ammonia or with soluble Prussian blue, and 

 strain through muslin. With the addition of a little thymol 

 the fluid will keep well if tightly corked. After in- 



