INFECTIOUS DISEASES. 75 



and growth of the specific germ. It travels in the air and seems 

 to attack the animal suddenly. 



The horse, donkey, mule, dog, as well as man, may become 

 affected. 



Give the pathology of influenza. 



Lesions peculiar to this affection are not positive. The 

 mucous membrane of the stomach, more especially the pyloric end, 

 together with that of the small intestines, shows hyperemia, is 

 swollen and ecchymosed. The mucous membrane of the nasal 

 cavity and the larynx is swollen and congested. In other cases 

 the brain, spinal cord or spleen may show changes. 



What are the clinical features of this disease ? 



The fever, the catarrh, and the symptoms referable to the 

 nervous system. These conditions are independent of influenza, 

 and are each due to the infecting principle. One of these may be 

 more severe than the others; the fever is not the result of the 

 catarrhal inflammation, nor are the symptoms of the nervous sys- 

 tem the result of the other two. 



The gastric mucous membrane may be congested, and in some 

 cases that of the intestines ; there is usually more or less extensive 

 inflammation of the respiratory organs. 



The bronchial glands are enlarged and softened ; the right side 

 of the heart contains pale but firm clots, the bronchial mucous 

 membrane is reddened and cedematous. Hemorrhage into the eyes, 

 lungs, and brain may take place. 



What is the period of incubation ? 



It varies from about twenty-four hours to six or seven days. 



Give some of the most important symptoms. 



On account of influenza assuming numerous forms, the symp- 

 toms will vary accordingly. This disease is remarkable for the vari- 

 ety of symptoms. 



Simple or catarrhal influenza, the most common form, comes 

 on suddenly, in some cases preceded by a chill; there is loss of 

 appetite, a cough, a congestion of the mucous membrane of the 

 nose and eyes, which is swollen, reddened, and dry at the onset, 

 causing sneezing or snorting, soon to become moist from the secre- 

 tion, at first thin and watery, later becoming thicker and pus-like. 

 From this redness and tumefaction of the mucous membrane of eye 

 the disease has been called pink-eye. The eyes are half-closed, 



