DILATATION OF THE HEART. 



333 



wall yields to the pressure of the blood ; but the cause which most 

 frequently deprives the cardiac parietes of their tenacity is degenera- 

 tion of its tissues and in particular fatty degeneration. 



After the subsidence of the collateral cedenia which remains after 

 the abatement of an inflammatory affection of the heart, the muscles 

 of the organ may regain their power of resistance, and the dilatation 

 may be repaired. In other instances hypertrophy follows upon dilata- 

 tion. The dilatation arising from typhus, or protracted chlorosis, usual- 

 ly disappears when the attenuated muscular fibres of the heart, with 

 the rest of the muscles, recover their proper condition. On the con- 

 trary, the dilatation proceeding from degeneration of the substance of 

 the heart, is incapable of repair, and, indeed, always grows worse as it 

 grows older. 



3. Dilatation may proceed from the degeneration of the substance 

 of an excentrically hypertrophied heart. This transition from hyper- 

 trophy to dilatation occurs quite as often as does the transformation 

 above alluded to from dilatation to hypertrophy ; and, indeed, it often 

 happens that both metamorphoses take place in the same patient at 

 different periods of the disease. Thus it can be shown that a valvular 

 derangement first gives rise to dilatation ; and that this is subsequent- 

 ly converted into a hypertrophy, which compensates for the deficiency 

 of the valve ; and that at last the substance of the heart undergoes 

 degeneration, and the hypertrophy is again replaced by dilatation, 

 whereupon the compensatory action ceases. The latter dangerous 

 transformation often does not take place until long after the valvular 

 disease has been established. So, too, in emphysema ; years may 

 elapse ere the excentric hypertrophy of the right ventricle, which com- 

 pensates for the obstruction of the pulmonary circulation, changes into 

 dilatation, to the great detriment of the patient. Nevertheless, it 

 would seem that a certain period of continued overaction of the heart 

 suffices to determine the conversion of a true hypertrophy into a spuri- 

 ous one, a circumstance which has not been observed to occur in other 

 overworked muscles. Degeneration of the hypertrophied cardiac mus- 

 cles is much accelerated if the patient's nutritive condition be allowed 

 to deteriorate. One of the most common of the diseases of aged and 

 decrepit people is an excentric hypertrophy of the left side of the heart, 

 caused by endarteritis deformans, which, when of long standing, grad- 

 ually changes into dilatation by degeneration of its muscular sub- 

 stance. These are the cases to which people allude when they speak 

 of enlargement of the heart as being one of the most severe and dan- 

 gerous of the maladies of that organ, and which is the most terrible 

 bugbear of many old people. 



ANATOMICAL APPEARANCES. Care must always be taken riot to 



