RABIES 



653 



the passage of the virus through twenty-one to thirty rabbits, in this 

 way, will reduce its incubation time to seven or eight days. Babes 

 claims to obtain a virus fixe more rapidly by passing the virus alter- 

 nately through rabbits and guinea-pigs. 



For pm-poses of inoculation, virus is prepared by emulsifying in 

 sterile salt solution pieces of the medulla or cerebellum of animals dead of 



Fig. 153. — Method op Drying Spinal Cobd of 

 or Attenuation. 



Rabbit tor Purposes 



a previous inoculation. The brain tissue which is not emulsified may be 

 preserved under sterile glycerin in a dark and cool place for furthemse. 



II. Rabbits are inoculated with virus fixe by intracranial injection. 

 A small incision is made in the shaved scalp in the median line, and the 

 skin is retracted. With a small trephine or a round chisel, an opening 

 is made in the skull in the angle between the coronary and sagittal su- 

 tures. Through this opening about 0.2 to 0.3 c.c. of the virus fixe is in- 

 jected, either directly into the brain substance or simply imder the dura. 



As soon as a rabbit so inoculated has died it is autopsied. The 

 animal before dissection should be washed in a disinfectant solution 

 — lysol or carbolic acid. The skin is then removed and the animal, 

 lying on its ventral surface, is fastened to a dissecting board. The 

 spinal canal is then laid open with a pair of curved scissors and 

 the spinal cord carefully removed. This is accomplished by cutting 

 across the cord in the liunbar region, and lifting this with a forceps 

 while the nerve roots are divided from below upward. 



The cord is suspended by a sterile thread within a large bottle into 

 the bottom of which pieces of potassium hydrate have been placed. 

 The bottle is then set away in a dark room or closet, the temperature of 



