170 MICROBIOLOGY 



usually enlarged and sprinkled with grayish nodules. Other 

 organs may be involved. 



Rabies. When inoculations are necessary to make a 

 diagnosis, a rabbit, guinea pig or dog is injected beneath the 

 dura with a bit of the brain or spinal cord of the suspected 

 rabid animal. The guinea pig is reported by some to respond 

 more promptly, but in our experience the subdural inocula- 

 tion of rabbits has been the most reliable. The subdural 

 method is, briefly stated, as follows : 



The brain of the suspected animal is removed with 

 aseptic precautions as soon as possible after death. A small 

 piece of the brain or spinal cord is placed in a sterile mortar 

 and thoroughly ground with a few cubic centimeters of ster- 

 ilized water or bouillon. This forms the suspension to be in- 

 jected. The hands of the operator and all instruments are 

 carefully disinfected. The rabbit is etherized, the hair clipped 

 from the head between the eyes and ears, and the skin thor- 

 oughly washed and disinfected. A longitudinal incision is 

 then made, the skin and subcutaneous tissue held back by 

 means of a tenaculum, a crucial incision is made in the perios- 

 teum on one side of the median line to avoid hemorrhage from 

 the longitudinal sinus, and the four corners of the periosteum 

 reflected or pushed back. By the aid of a trephine a small 

 button of bone is easily removed, leaving the dura mater ex- 

 posed. With a hypodermic syringe a drop or more of the 

 rabid brain suspension is injected beneath the dura, the peri- 

 osteum is replaced, the skin carefully sutured and disinfected^ 

 and the rabbit returned to its cage. As soon as the influence 

 of the anesthetic has passed off, the rabbit shows no appear- 

 ance of discomfort. If the operation is performed in the fore- 

 noon, the animal partakes of its evening meal with the usual 

 relish. The inoculation wound heals rapidly and the rabbit 

 exhibits every appearance of being in perfect health until the 

 beginning of the specific symptoms, which occurs ordinarily 

 in from 12 to 30 days, usually in 17 to 20 days, after the 

 inoculation. Occasionally the symptoms appear earlier than 



