DILATATION OF THE HEART. 335 



tion more laborious, since, although its power is not diminished, the 

 amount of blood which it must expel is increased. Hence, the effect 

 of dilatation upon the distribution and force of the circulation is pre- 

 cisely the reverse of that of hypertrophy. However, as long as the 

 substance of its walls remains healthy, the organ still continues capa- 

 ble of fulfilling its function, by dint of increased exertion, just as a 

 healthy heart overcomes obstacles to the circulation by greater energy 

 of its contraction. It is very different, however, when dilatation of the 

 heart is accompanied by degeneration of its muscles, as it is then un- 

 able to sustain such augmentation of its functional energy. Its action 

 is insufficient, and the consequences of this defective action become 

 recognizable in derangement of the circulation which ensues. The 

 amount of blood expelled from the heart being too small, the arteries 

 are inadequately filled, their walls contract, and the size of the indi- 

 vidual vessels is reduced. The consequence of the diminution of the 

 arterial contents is an augmentation of that of the veins ; but, as the 

 number of the veins exceeds that of the arteries, the filling of the in- 

 dividual veins never increases in proportion as that of the arteries di- 

 minishes. Moreover, a part of the blood which should occupy the 

 arteries is in the dilated and half-emptied heart. Accordingly, the 

 signs of deficience of blood in the arterial system appear earlier and 

 in slighter degrees of the disease than do the symptoms of engorge- 

 ment of the venous system. The capillaries also become abnormally 

 full, owing to the impediment to their circulation offered by the en- 

 gorgement of the veins, while the tension of the arterial walls, even 

 when the vessels are imperfectly filled, still exceeds that of the capil- 

 laries, so that the blood continues to flow into them. Finally, the 

 quantity of blood set in motion by each systole being abnormally 

 small, the circulation is retarded, and the blood acquires a more venous 

 character, owing to the greater quantity of carbonic acid which it re- 

 ceives, and because it does not return so often to the lungs to obtain 

 oxygen. 



When dilatation of a part of the heart is complicated by valvular 

 disease, emphysema, or any other affection of the lungs by which the 

 circulation is impeded, it is often difficult to decide whether and how 

 much the lack of blood in the arteries, the venous engorgement, the 

 retardation of the circulation, and the venous state of the blood, de- 

 pend upon the primitive disease, and how much upon the dilatation. 

 (Thus, Traube ascribes the dropsy of pulmonary emphysema to dilata- 

 tion and degeneration of the right heart alone, and not to destruction 

 ol' a large number of the pulmonary capillaries ; while, in my opinion, 

 both of these causes are to be taken into account, and the dropsy of 

 emphysema is only to be dreaded when disorder of the pulmonary cir 



