33i DISEASES OF THE HEART. 



mistake a heart distended by blood and relaxed from putrefaction for 

 a dilated heart. Advanced decomposition of the rest of the body, ex- 

 treme softness of the substance of the heart, and its saturation with 

 the coloring matter of the blood, are the distinctive marks in such 

 cases. When the dilatation involves the entire organ, its form is 

 changed in the manner described m speaking of hypertrophy of the 

 heart. As, however, in most cases the dilatation is partial, and far more 

 frequently involves the right side of the heart than the left, a dilated 

 heart usually appears wider without any corresponding increase in 

 length. When the wall of the dilated organ seems thinned, the de- 

 gree of thinning must be accurately determined by measurement, as 

 otherwise there will be danger of error. General statements, such as 

 " moderate thinning " or " moderate thickening " of the walls of the 

 heart, are of no value whatever. When the wall of the left ventricle 

 is thinned, it collapses when cut open. This does not occur when the 

 organ is in normal condition. In cases of great dilatation of the auri- 

 cles, the muscular fasciculi may be so widely separated that the walls, 

 in places, have a membranous appearance. When the ventricles are 

 much dilated, with wasting of the muscular substance, we sometimes 

 find some of the trabeculse reduced to the condition of fleshless ten- 

 dinous cords. 



When the wall of a dilated ventricle is thickened, it is sometimes 

 possible to recognize that the hypertrophy is of the spurious kind, 

 merely from the color and resistance of its substance. In other in- 

 stances, the tissues of the heart appear normal upon cursory examina- 

 tion ; but the general dropsy, and other signs of engorgement, which 

 are not ascribable to valvular disease, or to other obstacle to the circu- 

 lation, give proof of the abnormal state of the muscular substance of 

 the heart, and microscopic examination reveals its degeneration. At 

 other times the microscope exhibits a much slighter degree of degen- 

 eration of the substance of the cardiac wall than the intensity of the 

 venous engorgement would lead one to suspect. As this latter condi- 

 tion, when unaccompanied by obstruction to the course of the circula- 

 tion, is a most positive sign of lack of functional power in the heart, I 

 feel warranted in making the following assertion, based upon a large 

 number of accurate observations : that it is not possible, by means of 

 the microscope, to recognize all the alterations of the muscular fibrillae, 

 which diminish the functional power of the heart. 8 



Notwithstanding that the orifices of the heart also take part in the 

 dilatation, the valves still remain capable of closing perfectly, in con- 

 sequence of their enlargement, which keeps pace with their thinning, 

 and owing to elongation of the chordae tendineae. 



SYMPTOMS AND COUBSE. Dilatation of the heart renders its ao 



