USE OF ANIMALS 171 



15 days and in some cases the rabbits are not attacked for 

 from 1 to 3 months. 



The symptoms following the inoculations are quite uni- 

 form, the only pronounced difference being in the length of 

 time the rabbits live after the initial manifestation of the 

 disease. The fact should be clearly stated that rabbits do not 

 ordinarily become furious. In some instances they are some- 

 what nervous for a day or two preceding the paralysis. There 

 appears to be a marked hypera3sthesia. Usually the first indi- 

 cation of the disease is a partial paralysis of one or both hind 

 limbs. This gradually advances until the rabbits are com- 

 pletely prostrated, the only evidence of life being a slight 

 respiratory movement. The head occupies different positions. 

 In some it is drawn back as in tetanus ; in others it is drawn 

 down with the nose near the forelegs ; and in still others it is 

 extended as if the animal were sleeping. The period of this 

 complete paralysis varies from a few hours to a few days, but 

 ordinarily it does not exceed 24 hours. Although the animals 

 are unable to move voluntarily, there is usually a reflex action 

 of the limbs until a very short time before death. 



During the period of incubation the temperature of the 

 rabbits remains normal. As the time approaches for the first 

 symptoms to appear there has been in the animals tested an 

 elevation of temperature of from 1 to 2 degrees, which con- 

 tinued for a variable length of time, but rarely longer than 

 2 days. This is followed by a gradual or usually a more 

 rapid drop to the subnormal, which continues to the end. 



Swine plague. Rabbits are most susceptible. Inoculate 

 subcutaneously with a bit of the pneumonic tissue, either in a 

 solid piece or in a suspension in bouillon hypodermically. In 

 case of virulent swine-plague bacteria, the rabbit will die in 

 from 16 to 36 hours from septicemia. Pure cultures can be 

 obtained from the blood, spleen, liver, or kidney. Stained 

 cover-glass preparations from these organs show a greater or 

 less number of polar-stained bacteria. 



In case of a more attenuated virus the rabbit will live 

 from a few days to several weeks and possibly months. In 



