THE PASTEUR TREATMENT 613 



The longer the drying-out process is allowed to go on the more 

 attenuated becomes the virus. 



The emulsion used in inoculating rabbits and also in the protective 

 inoculations is always prepared from the cords of rabbits containing 

 the fixed virus by rubbing up pieces of the cord with sterile physio- 

 logical salt solution until a milky emulsion is obtained. It is, of course, 

 always necessary first to start from the cord of a hydrophobic dog 

 and to continue inoculating rabbits subdurally until a fixed virus has 

 been obtained. 



Technique. The technique of subdural inoculation in rabbits is as 

 follows: The animal is fastened to a small animal operating table, 

 resting on its abdomen, and the head is fixed so that it cannot move. 1 

 The scalp is then cut open very near the median line from near the 

 posterior angle of the eye toward the insertion of the ear. The 

 periosteum is next removed from the bone. The latter is then per- 

 forated by a small trephine, the tip of which is not more than about 

 2 to 3 mm. in diameter. The piece of bone cut out is removed by a 

 small hook. The dura mater then becomes visible and it is perforated 

 by the fine needle of a hypodermic syringe and from i to J c.c, of 

 the emulsion is slowly injected into the subdural space. In inserting 

 the needle it should be held rather obliquely and directed forward and 

 outward; in this manner injury to the brain is avoided. After the 

 emulsion has been injected and the needle withdrawn the linear 

 incision of the scalp is closed by sutures and a collodion dressing is 

 put on the wound. It goes without saying that everything has to be 

 done aseptically in order to avoid the occurrence of a septic menin- 

 gitis which might kill the experimental animal before rabies had time 

 to develop. This generally occurs nine to twenty-one days after the 

 inoculation of the street virus and six to seven days after the inoculation 

 of the fixed virus. The subdural method is used exclusively in the 

 preparation of the fixed virus; it is the only reliable one, and it alone 

 should be used in diagnostic work. Even the intraocular method 

 is not absolutely reliable, and all other methods are very unreliable. 

 Rabbits inoculated with street virus generally develop the picture of 

 dumb rabies; however, this is not invariably the case, and they 

 sometimes develop the furious type, become aggressive, and are liable 

 to bite. Since the cases where hydrophobic rabbits did bite persons 

 all occurred in laboratories, and since the persons bitten all promptly 

 received treatment, it is not known whether such an injury might 

 lead to an outbreak of hydrophobia. 



Rabbits after being inoculated with street virus, before developing 

 typical symptoms, generally show, as first noticed by Babes, an 

 elevation of temperature. Others have denied that this prodromal 

 elevation of temperature regularly occurs. This is followed by a 



Kraus states that it is not necessary to tie rabbits to the operating table; they can be held 

 by an assistant and the operation can be performed. This saves much time if a number of 

 animals are to be inoculated. 



