86 DISEASES OF THE HEART 



edge of the valves. They propagate, produce irritation, and 

 assisted by the mechanical action of the valves, an active 

 inflammatory reaction is soon established. The inflammation 

 spreads to the other parts of the endocardium and may cause 

 a general endocarditis. The rapidity of the process depends 

 upon the virulency of the infection or the amount of the 

 toxins present. 



2. Spread of the inflammation from adjacent structures 

 or organs may produce the condition, such as from a myo- 

 carditis, pericarditis, pleuritis, or a pneumonia. 



3. There are several predisposing conditions which should 

 be considered: (a) Chilling the surface of the body, such as 

 exposure to cold, or cold baths, carelessness in thoroughly 

 drying the skin of animals after baths, etc., make them more 

 susceptible to infection by reducing resistance. 



(b) In old animals degenerative changes of the heart 

 muscle, valves, etc., make them less resistant. 



(c) Young puppies, chicks, kittens, from hereditary influ- 

 ences, often favor the development of the condition. 



(d) During convalescence from long-continued diseases 

 there is a predisposition to endocarditis. 



(e) Traumatic conditions over the region of the heart 

 (kicks, blows, fractured ribs, etc.). 



4. Mineral poisons (mercury, phosphorus, etc.) or some 

 drugs administered, in large doses, or for too long a period, 

 produce direct irritation to the endocardium, or predispose 

 to the condition. 



In the etiology of endocarditis, infection must always be 

 regarded as the principal causative factor. 



Necropsy.— Macroscopically two forms of acute endocar- 

 ditis are recognized, viz.: 



(a) Endocarditis Valmlaris Verrucosa.— This is charac- 

 terized by small enlargements, about the size of a millet 

 seed, on the free edges of the valves, on the tendons and 

 papillary muscles. They are nodular, wart-like in appear- 

 ance, grayish-white or whitish-yellow in color, and their 

 surface covered with blood-stained or colorless stratified 

 epithelium. These growths may develop into large polypous 

 proliferations, which often cause stenosis of the openings 



