MICROBIAL DISEASES OF MAN AND ANIMALS. 66 1 



and this is followed by paralysis and death, the relative length of the two 

 stages varying in different animals. In the dog the disease runs its course 

 in six to eight days. It begins with altered behavior of the animal, itching 

 of the infecting scar, changed appetite, and slight fever. The dog swallows 

 grass, stones, and pieces of wood. As the stage of excitement becomes 

 more fully developed the animal may run away and may travel fifty miles 

 or more, snapping and biting from time to time, as the fits seize him, every- 

 thing in his path. Finally the excitement is succeeded by paralysis, 

 beginning in the lower jaw which hangs down. Then the hind legs fail, 

 and soon the dog, no longer able to drag himself along, lies completely 

 paralyzed, greatly emaciated, and soon dies. In the rabbit the stage of 

 excitement is hardly noticeable, but the animal passes quickly into the 

 paralytic stage, dying in two or three days. This type of paralytic rabies 

 sometimes occurs in dogs, but is is more commonly observed in herbivor- 

 ous animals. 



In man there is at first psychical change, irritation in the scar of the 

 infecting wound and rise of temperature. The first diagnostic symptom 

 is usually a sudden spasm of the pharynx upon an attempt to swallow 

 water. This convulsive seizure is repeated upon every attempt to drink, 

 and soon even the sight of water or the thought of it brings on the attack. 

 The cramps extend to other muscles of the body, and the patient may 

 die in a convulsive seizure, or may pass into the succeeding paralytic 

 stage and die peacefully. The dread of water which is often so promi- 

 nent a symptom in man has given the name of hydrophobia to the disease. 

 Consciousness and general intelligence are not particularly affected. 

 The duration of the disease is from three to six days. 



Rabies can be transmitted with certainty by injecting a small amount 

 of emulsified spinal cord of the rabid animal into the brain of a rabbit 

 or guinea pig. Inoculation under the skin is not quite so certain, and in- 

 oculation into the blood stream, or by feeding, generally fails to transmit 

 the disease. When first removed from a rabid dog, the virus (street virus) 

 kills rabbits in from two to four weeks, but after repeated transfer from 

 rabbit to rabbit in series, the period of incubation is shortened until death 

 occurs quite regularly in six or seven days after inoculation. Beyond 

 this there is no further increase in virulence for rabbits, and this six- or 

 seven-day virus is called the "fixed virus." 



The localization of the virus in the body of the rabid animal has been 

 worked out by experimental inoculations. The central nervous system 



