1090 



Valvular Diseases. 



left side is displaced in dogs about 3-5 cm. or more upward, 

 while in other animals it is displaced upwards and backwards 

 and may reach as far as the seventh rib and beyond the middle 

 of the lower third of the chest. The first heart sound is clear, 

 but the diastolic sound is accompanied by a murmur which 

 is usually loud, blowing or roaring, perhaps rough or ringing, 

 prolonged, and which is separated from the systole by a rather 

 short pause. Its greatest intensity is, in all mammals, in the 

 left fourth intercostal space immediately below the shoulder 

 line (Fig. 193.2), although it may be heard, a little less clearly, 

 also in the same intercostal space on the right side. The 

 purely diastolic sound which originates in the Art. pulmonalis 

 can be heard in the region of the left ventricle in association 

 with the murmurs just referred to, but near the origin of the 



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A i\ l\ 



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Fig. 195. Sphygmograph of the abdominal aorta in the horse, a bounding pulse in 

 aortic insufBciency ; 6 pulse of a healthy horse (Time in 0.2").- 



pulmonary artery (left third intercostal space, 'lower half of 

 the lower third of the chest [Fig. 193.3] ) it may..be heard almost 

 alone. 



The pulse is characteristic. The hypertrophied left ventricle 

 forces an increased amount of blood into the arota and through 

 it into the peripheral arteries in which the return flow of tlae 

 blood during the preceding diastole had produced a very con- 

 siderable lowering of the blood pressure in comparison with 

 the normal. The increased amount of blood which is forced 

 out with every ventricular systole, and the greater difference 

 (compared with the normal) between the systolic and the 

 diastolic blood pressure in the arteries produce a more vigorous 



