290 CIRCULATOUY APPAEATUS. 



distinctly heard over the right edge of the sternum on a level with the 

 second intercostal space, inasmuch as the ascending limb of the aortic 

 arch lies in close proximity to the thoracic wall at this point (fig. 92, c). 

 The murmur is proj^agated into the arteries. Another series of pheno- 

 mena manifests itself during the diastole of the heart. The insufficiency 

 of the sigmoid valves allows a part of the blood which has just been 

 driven into the aorta to regurgitate, as the pressure in the left ventricle, 

 when it is relaxed, stands lower than that in the aorta. The familiar 

 diastolic click of the healthy valve is no longer heard; its place is taken 



Fig. 92. 



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' h-i:. 



<r 



'• /h3 



■'. .o 





Hypertrophy of left ventricle. Heart hi situ. a. Left mammary 

 line; 6. V. cava superior; c. Aorta; d. Bulb of pulmonary 

 artery; e. Eight auricle; /. Eight ventricle; g. Left auricle; 

 li. Left ventricle (normal size); o. Left ventricle (hyper- 

 trophied). 



by a second, diastolic murmur, most clearly heard over the heart's apex 

 towards which the returning blood-current is directed. A farther con- 

 sequence of the valvular insufficiency is the rapid collapse of the pulse 

 in the arteries ; the mechanism of the collapsing pulse in the present 

 rase being different from that in chronic endoarteritis. The chief danger 

 which threatens patients suffering from stenosis and insufficiency is 

 undoubtedly the lowering of the blood-pressure in the arteries, and 

 the consequent equalisation of the arterial and venous tension, 

 whose difference alone it is which renders the passage of the blood 

 through the capillaries possible. Hence the blood accumulates in 



