178 ACTIVE IMMUNIZATION 



desiccation, and that after twelve to fourteen days it is lost alto- 

 gether. The plan of treatment then is to inoculate the patient 

 on successive days with material of increasing virulence, beginning 

 with that which is altogether innocuous, i. e., twelve to fourteen 

 days old. 



The technique employed in the preparation of the virus and the 

 immunization of the patient, as described below, is that in use at 

 the Pasteur Institute of the College of Physicians and Surgeons of 

 Baltimore, under the direction of Dr. N. G. Keirle, and represents 

 the original Pasteur method. 



Preparation of the Virus. The original virus was obtained from the 

 Pasteur Institute of Paris, and had been started from the medulla 

 of a rabid cow in 1882. It has since been transferred from rabbit 

 to rabbit, and has now reached about the nine hundreth remove. 

 Another virus was started by Dr. Keirle himself from the medulla 

 of a rabid cow, and has reached about the six hundreth remove. 

 As a rabbit will live about twelve days after inoculation, about 

 thirty passages may be made in a year. 



The inoculations are made as follows: "The hair between a line 

 drawn transversely through the ears and eyes is cut off with scissors 

 and washed with a 3 per cent, solution of carbolic acid. No 

 anesthetic is required; the animal does not cry out, and evinces 

 no sign of pain. The animal need not be strapped down, but may 

 be held on the table by an assistant. A cut one inch and a quarter 

 long is made with the knife or scissors, longitudinally, through the 

 skin in the middle of the space at the top of the head between the 

 lines above named. A blepharostat keeps the incision apart, and 

 the sublying tissue is scraped away so as to expose the bone a little 

 to one side of the median line. The trephine has a diameter of 

 5 mm. and a ring guard which is set at 2 mm. from the cutting end 

 of the crown; the trephine may be a bit fastened in a revolving drill 

 handle, or a simple hand trephine made of metal rod 17 cm. long. The 

 button of bone is removed with a tenaculum and the dura is exposed, 

 and an ordinary hypodermic syringe is used to inject three or four 

 drops of the rabic emulsion beneath the dura. If the perforating 

 end of the needle is curved almost at a right angle for a space of 4 mm. 

 it facilitates its introduction, but this is by no means indispensable. 

 The wound is closed by interrupted suture (three are generally 

 sufficient) and then sealed with collodion. The ordinary suture 



