UTILIZATION OF ANIMALS FOR BACTERIAL DIAGNOSIS 239 



7. For the production of various antibodies, as antitoxins, agglu- 

 tinins, precipitins and lysins. 



The choice of animals depends chiefly upon the nature of the obser- 

 vation to be made. Rabbits, guinea-pigs, white rats and mice, dogs 

 and cats are more commonly made use of for these various examina- 

 tions. The method and site of inoculation, as well as the dosage, may 

 influence the course of the infection. 



The Inoculation of Animals. Animals may be inoculated through 

 natural channels, as by inhalation into the respiratory tract, or inges- 

 tion into the alimentary tract. More frequently, however, material is 

 introduced parenterally into the tissues direct. The site of inoculation 

 is usually the skin, the body fluids or body cavities. The skin must 

 necessarily be entered to reach the deeper tissues. For this reason 

 the site of injection should be shaved and sterilized with tincture of 

 iodin. 1 



Cutaneous Inoculation. (a) Cutaneous: Material is rubbed upon a 

 shaved area of skin. 



(6) Intracutaneous : Injection is made directly into the skin. 



(c) Subcutaneous: Material is introduced beneath the skin. A 

 pocket is sometimes made by separating the skin from the cellular 

 subcutaneous tissue, into which solid fragments of tissue are placed. 

 The skin over the abdomen is a common site for inoculation with fluid 

 cultures; the hypodermic needle is introduced at one side of the 

 median line and forced through the subcutaneous tissue in a trans- 

 verse direction, to a point well beyond the median line on the opposite 

 side. The abdominal wall becomes somewhat tense and does not 

 permit leakage to the outside if this procedure is followed. 



Intravenous inoculations are made either into the blood stream 

 through a vein, or directly into the heart. Rabbits are readily injected 

 through the marginal ear veins; the vein is pinched close to the head 

 of the animal and gently massaged; this causes distention and makes 

 the vein prominent. A hypodermic needle will then readily enter 

 the vein; it should be gently forced along its course for a centimeter 

 or two before injection. 



Body Cavities. The peritoneal cavity is commonly selected, but 

 intrapleural injections are readily made. Before introducing a hypo- 

 dermic needle into the peritoneal cavity, the animal, guinea-pig or 



1 Tincture of iodin should be freshly prepared and painted upon the dry surface it is 

 desired to sterilize. Sterilization is usually accomplished after two or three minute's 

 exposure to the iodin solution. 



