Diseases of the Heart and Organs of Circulation. 413 



beneath the wings but above all and most clearly over the 

 breast-bone. 



In disease these sounds may be heard in unusual situations, 

 they may be altered in force, duration or rhythm, or they may be 

 associated with other sounds or superseded by them. 



The sounds may be heard in new situations, in displacements 

 of the heart from tumors or effusions in the chest, structural 

 changes in the lungs, pleurae, or pericardium, aneurism of the 

 aorta, etc., etc. 



The heart sounds are clearly heard over any part of the chest 

 when the lung tissue intervening between that part of the surface 

 and the heart is solid (hepatized). They are heard distinctly 

 behind the median part of the right shoulder, when liquid effu- 

 sion into the left pleural sac has displaced the heart to the right ; 

 and when the right cavities of the heart are extensively dilated, 

 as exists so commonly in the advanced stages of ' 'heaves. ' ' 



The extent over which the sounds may be heard is increased 

 when the lung surrounding the heart is solidified (hepatisation, 

 splenisation, etc.), or when liquid effusion exists in the chest. 

 A liquid but more especially a solid is a better conductor of 

 sound than the spongy lung. Enlargement (hypertrophy) of 

 the heart equally increases the area of sound. The area of sound 

 is lessened by atrophy of the heart, and by an emphysematous 

 condition of the lungs by which the heart is more extensively 

 covered and further separated from the walls of the chest. 



The force or intensity of the heart sounds is increased in high 

 fever, in acute inflammation, in increase of the muscular walls of 

 the heart with enlargement of the in ternal cavities, in functional 

 disturbance from fear or other exciting cause, and in palpitation. 

 Often in a weak and bloodless patient, the heart sounds can be 

 clearly heard at several yards distant from the animal. The 

 intensity of the sounds is diminished in debility when not associ- 

 ated with palpitation, in atrophy of the muscular substance of 

 the heart, in hypertrophy of the muscular tissue of the heart 

 with diminution of its internal cavities, in broken wind when the 

 emphysematous lung more completely env elopes the heart, and 

 in cases of extensive liquid effusion into the pericardium which 

 prevents the apex of the heart from striking against the side of 

 the chest. 



