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 purposes of inoculation, virus is prepared by emulsifying in 

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



FIG. 153. METHOD OF DRYING SPINAL CORD OF RABBIT FOR PURPOSES 



OF ATTENUATION. 



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

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



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 under 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 lumbar 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 



