DETERMINING BIOLOGICAL ACTIVITIES OF BACTERIA 173 



With proper care mice or rats may be easily injected intravenously 

 if a sufficiently fine needle is used. There are four superficially placed 

 veins running along the tail, which stand out prominently when rubbed 

 with cotton moistened with xylol. Into these the injections are made. 



When inoculating rats or guinea-pigs with bacillus pestis the KoUe 

 vaccination method is used. The skin is merely shaved and a loopful 

 of the culture vigorously rubbed into the shaven area. 



The various forms of animal holders which have been devised are 

 rarely necessary in bacteriological work unless working unassisted, im- 

 mobilization of the animals being easily accomplished by the hands of a 

 skilled assistant. 



Autopsies upon infected animals must be carefully made. The ani- 

 mals are tied, back down, upon pans fitted in the corners with clamps for 

 the strings. They are then moistened either with hot water or with a 

 weak solution of carboUc acid, so that contamination by hair may be 

 avoided. A median cut is made, the skin is carefully dissected back, 

 and the body cavities are opened with sterile instruments. Cultures 

 may then be taken from exudates, blood, or organs under precautions 

 similar to those recommended below for similar procedures at autopsy 

 upon man. 



Inoculated animals should be, if possible, kept separate from healthy 

 animals. Rabbits and guinea-pigs are best kept in galvanized iron-wire 

 cages, which are fitted with floor-pans that can be taken out and cleaned 

 and sterilized. Mice majr be kept in battery jars fitted with perforated 

 metal covers. The mice should be supplied with large pieces of cotton 

 upon batting since they are delicately susceptible to cold. 



