ON INJECTION xxi 



V. ON INJECTION. 



The injection of coloured fluids into the blood-vessels or 

 duets of an animal renders them much easier to see, and to 

 follow to their distribution. 



The colouring matter used must not be soluble in, or 

 affected by, any of the fluids in which the specimen is after- 

 wards to be dissected, hardened, or preserved. The most 

 convenient are French blue, Prussian blue, vermilion, and 

 carmine. 



In the case of the larger animals, freshly prepared plaster 

 of Paris forms, if coloured, a convenient substance for injec- 

 tion : it soHdifies in the vessels, and so does not escape if a 

 vessel is accidentally cut during the dissection. 



For smaller animals, thick gum-water or white of egg 

 may be injected cold, or a jelly made of gelatin and water 

 injected warm : the animal should afterwards be put into 

 alcohol to harden the injection. If the animal is not to be 

 dissected after injection, water coloured with any of the above 

 pigments may be used with advantage, and this method is 

 particularly useful for the alimentary and excretory systems 

 of the liver-fluke. 



For injecting small animals, a suitable syringe consists of 

 a glass tube with an india-rubber cap fitted on one end, the 

 other end being drawn out to a point sufficiently fine to 

 enter the vessel to be injected. After the tube is drawn out 

 in the flame and cut off, its sharp edges must be slightly 

 rounded off by holding for a moment in the flame. Several 

 such cannulse of various sizes should be kept ready. 



For injecting larger animals, such as a rabbit, with plaster 

 of Paris, the blood must first be washed out of the vessels 

 by injecting warm salt-solution. The following apparatus is 

 necessary, and must all be placed on the table ready for use 

 before the animal is killed ; for the blood coagulates after 

 death so rapidly as to allow no time to look for instruments. 



1. Cannulse : glass ones are the most convenient ; they 

 should be of various sizes, to fit the several vessels which it is 

 proposed to inject, and each should have a slight constriction 



