172 



BIOLOGY AND TECHNIQUE 



in obliquely so as to avoid penetrating the abdominal wall and entering 

 the peritoneum. 



In making intraperitoneal inoculations, great care must be exercised 

 not to puncture the gut. This can be avoided by passing the needle 

 first through the skin in an oblique direction, then turning it into a posi- 

 tion more vertical to the abdomen and perforating the muscles and perito- 

 neum by a very short and carefully executed stab. 



Intravenous inoculations in rabbits are made into the veins running 

 along the outer margins of the ears. The hair over the ear is clipped and 

 the animal held for a short time head downward so that the vessels 

 of the head may fill with blood. An assistant holds the animal firmly in 



FIG. 53. RABBIT CAGE. 



a horizontal position, the operator grasps the tip of the ears with the 

 left hand, and carefully passes his needle into the vein in the direction 

 as nearly as possible parallel to its course. (See Fig. 50.) 



Mice are usually inoculated under the skin near the base of the tail. 

 They may be placed in a jar over which a cover of stiff wire-gauze is 

 held. They are then grasped by the tail, by which they are drawn up 

 between the side of the jar and the edge of the wire cover, so that the 

 lower end of the back shall be easily accessible. The skin is then wiped 

 with a piece of cotton dipped in carbolic solution and the needle is in- 

 serted. Great care must be exercised to avoid passing the needle too 

 close to the vertebral column. Mice are extremely delicate, and any 

 injury to the' spine usually causes immediate death. 



