204 BIOLOGY AND TECHNIQUE 



ficially 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 

 Kolle vacination 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 un- 

 assisted, immobilization of the animals being easily accomplished 

 by the hands of a skilled assistant. 



Autopsies upon infected animals must be carefully made. The 

 animals 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 carbolic 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 instru- 

 ments. 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 gal- 

 vanized iron-wire cages, which are fitted with floor-pans that can 

 be taken out and cleaned and sterilized. Mice may 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. 



The Bleeding of Animals. Animals are bled for the purpose of 

 obtaining either corpuscles, defibrinated blood or serum. 



In order to obtain small amounts of blood, that is about 5 or 

 10 c.c., from rabbits, the ear is shaved and had best be immersed 

 in warm water for a few moments in order to expand the vessels. 

 Gentle rubbing with alcohol is also advantageous. The rabbit is 

 then held with head hanging downward, and a broad needle of the 

 Hagedore needle type is thrust into the vein and withdrawn. The 

 drops can be caught directly in a centrifuge tube, or in the culture 

 media for which it is intended. All blood media should be incubated 

 for 24 hours and the contaminated tubes discarded. 



A better method is to take blood from rabbits and from guinea 

 pigs directly from the heart. If this is skillfully done the animals 

 can be repeatedly bled without being killed. For taking blood for 



