446 



DISEASES OF THE CIRCULATORY SYSTEM, 



as yet imperfectly known ; we are ignorant as to whether it be a 

 cause or a consequence of the nervousness of these subjects. 



2. "Vascular alterations which mechanically hinder the circula- 

 tion, determining a secondary cardiac hypertrophy, which is also 

 called symptomatic hypertrophy. 



Among these alterations we must mention : aneurisms of the 

 aorta ; congenital contraction, thrombosis, and the compression of 

 this vessel by neoformations ; atheromatous processes and arterio- 

 sclerosis. 



3. Valvular lesions and troubles of the circulation to which they 

 lead constitute the most frequent cause of cardiac hypertrophy. 

 This hypertrophy well deserves the attribute of compensatory/^ 

 for Nature produces it in order to remedy the circulatory troubles. 



4. Diseases of the lungs, emphysema, compression of both lobes 

 or of a single one by exudates or transudates, pleural adhesions,, 

 glandered or tuberculous interstitial processes, by stoppage of the 

 circulation in a part of the pulmonary vessels, increasing the blood- 

 pressure in the right heart, the walls of which become hyper- 

 trophied. 



5. Pericardiac adhesions, by the constraint which they exercise 

 upon the movements of the heart, produce also a greater activity 

 of this organ and its hypertrophy. 



6. Finally, chronic nephritis becomes almost fatally complicated 

 by cardiac hypertrophy. (Concerning the morbid sympathies exist- 

 ing between these two affections, see Chronic Nephritis.) 



Passive dilatation of the heart constitutes generally the final 

 stage of active dilatation. A time comes, in fact, when the hyper- 

 trophied heart no longer suffices for the exigencies of circulation ; 

 the blood pressure which is felt upon it dilates it mechanically. 

 Fatty degeneration, endocarditis, myocarditis ; the alterations of 

 the myocardium in cases of intense fever, infectious diseases,, 

 poisonings, anemia, etc., determine cardiac dilatation by the same 

 mechanism. A rapid passive dilatation may be produced in the 

 course of acute pulmonary affections in which serious troubles of 

 the circulation exist, and also a considerable elevation of the blood 

 pressure in the right heart. Chronic pulmonary diseases, on the 

 contrary, produce hypertrophy, except when the animals are ex- 

 tremely debilitated : in this latter case, on account of the want of 

 nutritive matters, a dilatation only is formed. 



Symptoms. Common cardiac hypertrophy and compensatory 



