92 ESSENTIALS OF BACTERIOLOGY 



rated from the rest and placed in a glass jar, which is partly 

 filled with sawdust and covered with a piece of wire gauze. 



Subcutaneous. The root of the tail of a mouse is used for 

 this purpose. The hair around the root of the tail is clipped 

 off, and with a pair of scissors a very small pocket is made in 

 the subcutaneous connective tissue, not wounding the animal 

 any more than is absolutely necessary, avoiding much blood. 

 The inoculating material is placed upon a platinum needle 

 and introduced into the pocket; solid bodies, with a forceps. 



To hold the mouse still while the operation is going on a 

 little cone made of metal is used. The mouse just fits in 

 here. There is a slit along the top in which the tail can be 

 fastened, and thus the animal is secure and immobile. 



Variously designed animal-holders are on the market and 

 used in laboratories. 



Intravenous Injections. Rabbits are very easily in- 

 jected through the veins. Mice are too small. 



The ear of the rabbit is usually taken. It is first washed 

 with i : 2000 bichlorid, which not only disinfects, but also 

 makes the vessels appear more distinct. The base of the ear 

 is compressed to swell the veins. Then a hypodermic 

 syringe, which can be easily sterilized, is filled with the de- 

 sired amount of virus, which is slowly injected into any one 

 of the more prominent veins present (Fig. 37). 



Intraperitoneal Injection. This is used with guinea- 

 pigs chiefly. The abdominal wall is pinched up through its 

 entire thickness, and the needle of the syringe thrust directly 

 through, so that it appears on the other side, then the fold 

 let go, the needle withdrawn just far enough so as to be within 

 the cavity. 



Inoculation in the Eye. The anterior chamber and the 

 cornea are the two places used. The rabbit is fixed upon a 

 board, the eyelids held apart and head held still by an assist- 

 ant. A few drops of cocain having first been introduced in 

 the eye, a small cut is made in the cornea. The material is 

 passed through the opening with a small forceps, and with a 

 few strokes of a spoon it is pushed in the anterior chamber. 



