144 RKICHKL : 



The manner in which the presence of the virns can be 

 demonstrated positively is as follows : Some of the saliva, or 

 any of the body flnids that may contain the virus, or a small 

 piece of the brain tissue, spinal cord, nerve ganglion or sali- 

 vary gland may be taken and ground in a sterile mortar and 

 an emulsion made and thinned out so that it can be drawn up 

 through a hyperdermic needle into a syringe. The emulsion 

 may or may not contain the virus. To demonstrate it pos- 

 itively, experimental animals are inoculated, generall}^ the 

 rabbit, but the guinea pig, cat or dog, or any of the warm 

 blooded animals may be used. An injection of a small por- 

 tion of the emulsion may be made directh' into the muscle 

 tissue or beneath the skin, but preferably beneath the mcningis, 

 or membranes covering the brain, which is very easily done 

 following the operation of removing a small piece of bone of 

 the cranium. The membranes covering the brain are then 

 pierced with the h^q^erdermic needle and a few drops of the 

 emulsion are forced beneath or between them. The skin at the 

 seat of the operation is sutured and then sealed with cellodin. 

 When the operation is carefully performed there is no pain, 

 and in many instances the animal will frolic and eat immedi- 

 ately after the operation. 



Like in all infectious diseases, a certain period elapses 

 between the time of the infection or the inoculation and the 

 appearance of the first symptoms of the disease, and this is 

 what is known as the period of incubation, and in rabies this 

 period varies with the different species of animals, to some 

 extent with animals of the same species, and varies also with 

 the location of the point of infection, as for example: A 

 rabbit inoculated by placing the virus directly beneath the 

 coverings of the brain will show s\Mnptoms of rabies in a 

 much shorter time than a rabbit inoculated beneath the skin 

 over the abdomen. For the same reason, a bite on the face is 

 considered more dangerous than one on the hand, and one on 

 the hand more dangerous than one on the foot. 



The period of incubation in dogs varies from 15 to 6(i days. 



