168 MICROBIOLOGY 



and forceps should be made as frequently as they become in- 

 fected. When organs are examined the portions of the sur- 

 fa3e through which an incision is to be made must be steril- 

 ized, if there is danger that the surrounding cavity is infected, 

 by searing it with a spatula which has been heated to a white 

 heat. Tissues if removed from the body should be placed 

 immediately under cover to avoid contamination. Sterile 

 deep Petri plates are useful for this purpose. 



When it is necessary to transport tissues some distance 

 they should be wrapped in cloths moistened in mercuric bi- 

 chloride or placed in sterile retainers and sent to the point of 

 'destination as soon as possible. They should also be kept cool 

 by packing the vessel containing them in a pail of ice. 



Animals rarely show the same gross lesions as man when 

 both suffer from the same disease. The cell changes are sim- 

 ilar, and, also, so far as we can test them, the curative or 

 immunizing effects of protective serums when administered in 

 proper doses. 



Animal inoculations for purposes of diagnosis. For 

 :simple diagnostic work with animal tests the guinea pig and 

 rabbit are most usually employed. Other species, however, 

 are not excluded. In preparing the animal for inoculation the 

 liair should be removed over the area of operation by the use 

 of scissors, and the skin washed and disinfected. A 5% 

 solution of carbolic acid or a solution of corrosive sublimate, 

 1 to 1000, may be used. The incision should be made with a 

 sharp knife. Liquid material is usually injected with a 

 hypodermic syringe. An anesthetic should be given when- 

 ever the pain inflicted is to be long continued or excessively 

 severe. The place of inoculation should be chosen where a 

 local swelling, infiltration of tissue, or abscess would not in- 

 terfere with the animal's locomotion. 



