DISEASES OF THE CIRCULATORY SYSTEM. 189 



CHRONIC AFFECTIONS OF THE HEART. 



ENLARGEMENT OF THE HEART.— Hypertrophy and 

 Dilatation. — Enlargement of the heart may result from 

 increase in size of the muscular walls, or from increase in 

 the capacity of the cavities. When the heart is hyper- 

 trophied without any alteration in the capacity of the 

 cavities, the condition is termed swifple hyijertrojphy. When 

 there is increase of capacity of the cavities, without enlarge- 

 ment or multiplication of the muscular elements or thinning 

 of the walls, it is termed simiole dilatation. When the 

 muscular structure is increased, and there is also increase in 

 the capacity of the cavities, it is termed ' hypertrophy with 

 dilatation,' or eccentric hyiJertro][)hy. It is doubtful if h^^Der- 

 trophy with diminution of cardiac capacity occurs, but it 

 has been mentioned under the term concentric lujjyertrojjJiy. 



Etiology. — Hypertrophy with or without dilatation may, 

 in most instances, be regarded as a compensatory condition, 

 owing to some obstruction to the circulation. It may be 

 induced by long-continued overwork ; and in hunters and 

 racers hypertrophy, or hypertrophy with dilatation, is of 

 frequent occurrence. Hypertrophy may also result from 

 frequently recurring or persistent palpitation. 



The obstruction to the circulation may occur at the 

 cardiac orifices, or at the orifices of the large arteries, 

 especially at the mitral and aortic openings. The obstruc- 

 tion to the blood- flow may be in the pulmonary circuit, as 

 in bronchitis and emphysema, and occasionally it may be 

 in other organs. Dilatation with hypertrophy is a frequent 

 result of aortic or mitral incompetence, owing to the re- 

 gurgitation of the blood. 



Symptoms. — Vary widely, according to the seat and 

 extent of the enlargement, and to the diseases with which 

 it is associated. 



