EXPERIMENTS UPON ANIMALS. 71 



CHAPTER XY. 



EXPERIMENTS UPON ANIMALS. 



THE smaller rodents and birds are the ones usually employed 

 for inoculation, as rabbits, Guinea-pigs, rats and mice, and 

 pigeons, and chickens ; sometimes monkeys. These are pre- 

 ferred, because easily acted upon by the various bacteria, readily 

 obtained, and not expensive. 



The white mouse is very prolific and easily kept, and is there- 

 fore a favorite animal for experiment. It lives well upon a little 

 moistened bread. A small box, perforated with holes, is filled 

 partly with sawdust, and in this ten to twelve mice can be kept. 

 When the female becomes pregnant she should be removed to 

 a glass jar until the young have opened their eyes, because the 

 males, which have not been raised together, are apt to attack 

 each other. 



Guinea-pigs. When Guinea-pigs have plenty of light and 

 air they multiply rapidly. Therefore it is best to have them in 

 some large stall or inclosure. They can be fed upon all sorts of 

 vegetables and grasses, and require but little attention. 



Methods of Inoculation. L Inhalation. Imitating the natural 

 infection, either by loading an atmosphere with the germs in 

 question or by administering them with a spray. 



II. Through Skin or Mucous Membrane. 

 U. With the Food. 



Method of Cutaneous Inoculation. The ear of mice is best 

 suited for this procedure. A small abrasion made with the 

 point of a lancet or needle, which has been dipped in the virus. 

 The animal is then separated 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 mice 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 absolutely necessary, avoiding much blood. The 

 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. 



