DISEASES OF THE RESPIRATORY ORGANS. 593 



(h'stinct, or even entirely absent, in round-chested and fat ones. 

 Diminished impulse, when not due to the above cause, indicates 

 feebleness of the heart's action from disease, as fatty degene- 

 ration of its muscular tissue ; hydrops pericardii, when the apex 

 may be prevented by the effusion from coming into contact 

 with the thoracic wall ; or it may arise from weakness of the 

 system generally, attenuation of the cardiac walls, and dilatation 

 of the cavities. Emphysema of the lungs may also diminish 

 the impulse, the enlarged lung overlapping the heart; and 

 adhesions of the pericardium to the pleuree of opposite sides may 

 bind down the heart so that the impulse will not be felt. 



The impulse of the heart is temporarily increased by any cause 

 of excitement, fear, exercise, fever, or pain. When excessive it 

 is called palpitation. 



Increased impulse, when not traced to the above-named 

 causes, or when it is easily induced, may depend upon organic 

 disease of the heart. It is stronger than natural in hypertropliy 

 of the cardiac walls, and particularly so if such hyjiertrophy is 

 associated with dilatation. It may, in such cases, be slow, 

 gradual, and double, and this kind of impulse is due to no 

 other condition of the heart; indeed it is one of those few 

 symptoms which throw light upon the condition of parts within, 

 for, notwithstanding much observation carefully recorded, we 

 are bound to confess that, unless cardiac diseases be aggravated, 

 we are unable, either by the character of the sounds or impulse, 

 to diagnose them with that certainty arrived at by those who 

 practise on the human patient. 



MORBID SOUNDS. 



1. A to-and-fro friction murmur, synchronous with the heart's 

 movements, indicates pericarditis or pericardial effusion. 



2. A bellows murmur with the first sound indicates mitral 

 insufficiency ; stricture of aortic orifice ; disease of the aortic 

 valves, or deposits on the ventricular surface of tlie mitral 

 valves ; or it may depend upon an altered condition of the blood 

 itself, as in anoemia, in which case it resembles a churning sound, 

 heard also in the large veins and arteries. Tliese anaemic 

 murmurs vary with the condition of the blood. Sometimes 

 there is a continuous hum heard at the base of the jugulars, and 

 to which the French have applied the term " hruit de diaUe." 



2q 



