RABIES 605 



incubation rather long. Three to seven weeks is the usual 

 time for development in dogs. However, some cases 

 develop only after several months. The period of incu- 

 bation in cats and fowls is usually shorter than in dogs. 

 The period of incubation is usually shorter in young animals. 

 The toxicity of rabies virus and the pathogenic action on 

 the tissues are no doubt due to some chemical product which 

 up' to the present has not been determined. 



Pathology. The disease is really characterized by the 

 absence of any marked gross pathological findings. The 

 lesions vary somewhat in individual cases. The digestive 

 tract shows congestion and hyperemia. The stomach may 

 be contracted and empty, or is frequently partially filled 

 with foreign material such as stones, straw, sticks, splinters 

 of wood, hair, feathers, etc. The folds of the mucous mem- 

 brane are markedly congested on their summits. Hemor- 

 rhage sometimes occurs from the foreign material cutting 

 or tearing the mucosa. The mucosa of the pharynx and 

 larynx shows congestion and is covered with mucus. An 

 acute catarrhal inflammation of the respiratory passages 

 is frequently found. The brain and its coverings are often 

 injected with small hemorrhages. No other lesions of any 

 importance are observed. 



Symptoms. From a clinical standpoint it is necessary 

 to divide rabies into two types, viz: (1) Furious rabies, 

 and (2) dumb rabies. The different train of symptoms 

 depends entirely upon whether the brain or spinal cord is 

 primarily involved. However, cases are observed occa- 

 sionally where an animal affected with dumb rabies suddenly 

 develops the furious type. The dumb or mute rabies seems 

 to be the most common form in the United States. 



1. FURIOUS RABIES. In this form three stages of devel- 

 opment are rather sharply defined : (a) Melancholic or pro- 

 dromic stage; (b) maniacal or irritative stage; (c) paralytic 

 stage. 



(a) Stage of Melancholy. In the stage of melancholy or in 

 the beginning of the disease, the first thing usually noted by 

 the owner is the altered behavior of the animal. It becomes 

 sullen, afraid, seeks dark places, is easily irritated, restless and 



