1086 Valvular Diseases. 



Occurrence. Since valvular lesions occur most frequently 

 in consequence of chronic endocarditis which is most common 

 in dogs, the valvular troubles are found most often in these 

 animals. (xVccording to Cadiot 5% of dogs over one year old 

 suffer from valvular disease; among 793 dogs autopsied by 

 Johne, chronic endocarditis was found in 4.3%, and among 

 1,831 dogs which were examined in the pathologic-anatomical 

 institute in Budapest 3.9% were found with evidences of 

 endocarditis). Next in frequency are horses, and tlien, very 

 much less often, the other mammalians, if the cases of acute 

 endocarditis are not included. The observations of Larcher 

 and Hartl show that valvular diseases are not infrequent in 

 fowls, although they give rise to functional heart disturbances 

 comparatively rarely. 



Etiology. Valvular heart lesions may be caused by the 

 following diseases of the heart: 



1. Acute Endocarditis (see p. 1078), which in its less rapid 

 cases takes a course presenting tlie clinical picture of valvular 

 disease. 



2. Chronic Endocarditis (Endocarditis valvularis chron- 

 ica). This disease is the basis for most cases of valvular 

 troubles and develops, probably principally, out of the acute 

 inflammation; it either occurs thus that, after the acute endo- 

 carditis has run its course, a proliferation with subsequent 

 atrophy of the connective tissue takes place, or thus that an 

 acute inflammation, which is not very intense of itself, recurs 

 periodically and produces proliferation and atrophy of con- 

 nective tissue after each recurrence. Accordingly all causes 

 and conditions which stand in etiological relation to acute 

 endocarditis may occasionally also lead to a chronic inflannna- 

 tion. In this respect those factors especially enter into con- 

 sideration which usually, or at least occasionally produce a 

 mild acute inflammation. This is particularly the case in 

 endocarditis following upon articular rheumatism and upon 

 croupous pneumonia, also in inflammation due to tuberculosis 

 and to erysipelas. In other cases the inflammation is chronic 

 from the beginning and is usually hot noticed; and in such 

 cases an infection may be a causative factor, although it does 

 not give rise to acute symptoms. Further, chronic endocarditis 

 develops in connection with chronic endoarteritis and arterio- 

 sclerosis, and in dogs frequently in association with chronic 

 interstitial nephritis. Sonnenberg found the mitral valve of 

 a cachectic tuberculous cow thickened and covered with a 

 yellowish-gray deposit, while the endocardium of the left heart 

 showed diffuse grayish-yellow discoloration. Hartl found in 

 chickens repeatedly a chronic endocarditis the origin of which 

 could not be determined. Lastly, severe exertion or the 

 mechanical irritation of the valves which is necessarily exerted 

 by it upon them, and also cold are said to produce the disease. 



