302 Veterinary Medicine. 



In disease these sounds may be heard in unusual situations, 

 they may be aUered in force duration or rythm, 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 associated with other sounds or superseded by them.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 be- 

 hind the median part of the right shoulder, when liquid effusion 

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

 when the right cavities of the heart are extensively dilated as ex- 

 ists 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 increa.ses 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 internal 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 distance from the animal. The zVz- 

 tensity of the sounds is diminished in debility when not associated 

 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 wi?id when 

 the the emphysematous lung more completely envelopes the 

 heart, and in cases of extensive liquid effusion into the pericar- 

 dium which prevents the apex of the heart from striking against 

 the side of the chest. 



The regular rythm, normally manifested by the two sounds 

 and the silence, may be modified in the unequal irregular or in- 



