MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 815 



tion, 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, everything 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 alon^, lies completely paralyzed, greatJy emaciated, 

 and soon dies. In the rabbit the stage of excitement is hardly notice- 

 able, but the aninjal passes quickly into the paralytic stage, dying after 

 two or three days. This type of paralytic rabies sometimes occurs in 

 dogs, but is more commonly observed in herbivorous animals. 



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

 infecting wound and rise of temperature. The first diagnostic Symp- 

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

 swallow water. This convulsive seizure is repeated upon every at- 

 tempt to drink, and soon even the sight of water or the thought of it 

 brings on the attack. The cramps extend to otber 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 prominent a symptom in man has given the name of 

 hydrophobia to the disease. Consciousness and general intelligence 

 are not particularly affected. The duration of active symptoms 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 inoculation into the blood stream, or by feeding, generally 

 fails to transmit the disease. When first removed from a rabid dog, 

 the virus (Street virus) kiUs rabbits in from two to four weeks, but after 

 repeated transfer from rabbit to rabbit in series, the period of incuba^ 

 tion 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 virus in the body of the rabid animal has been 



