DISEASES OF THE HEART. 91 



Exact position of the heart. — " A line," says Dr. Hope, " drawn 

 from the inferior margins of the third ribs, across the sternum, passes 

 over the pulmonic valves a little to the left of the mesial line, and 

 those of the aorta are behind them, but almost half an inch lower 

 down. A vertical line coinciding with the left margin of the ster- 

 num has about one-third of the heart, consisting of the upper portion 

 of the right ventricle on the right, and two-thirds, composed of the 

 lower portion of the right ventricle, and the whole of the left, on the 

 left. The apex beats between the cartilages of the fifth and sixth 

 left ribs, at a point about two inches below the nipple, and an inch 

 on its sternal side." 



*' Take the fifth costal cartilage on the leftside," says Dn Latham, 

 " and let a point midway between its junction with the sternum and 

 its junction with the rib be the centre of a circle, two inches in 

 diameter. This circle will, as nearly as possible, define the space 

 of the praecordial region, which is naturally less resonant than the 

 rest." 



Relatioti of the sounds to the state of the heart. — " A clearer 

 sound," says Dr. Latham, " proceeds from a thin heart ; and a 

 duller sound from a thick heart ; a sound of greater extent from a 

 large heart, and a sound of less extent from a small heart. A more 

 forcible impulse is given by a thick heart, and a feeble impulse by a 

 thin one ; the impulse is conveyed to a longer distance from a large 

 heart, and to a shorter distance from a small heart."* 



" Sounds and impulses," continues Dr. Latham, "are the inter- 

 preters of each other. The true meaning of the sound is tested by 

 the impulse, and the true meaning of the impulse is tested by the 

 sound. Thus, from a clearer sound, we argue only the probability 

 of an attenuated heart, but we argue its certainty from a clearer 

 sound, joined with a weaker impulse. From a stronger impulse we 

 argue only the probability of an hypertrophied heart; but we argue 

 its certainty from a stronger impulse joined with a diminished sound. 

 When impulse and sound increase together, there is probablj^lj^ 

 hypertrophy, but the heart is only acting more forcibly from pure 

 excess of nervous energy. When impulse and sound decrease 

 together, there is probably no atrophy, but the heart is only acting 

 more feebly from pure defect of nervous energy. When the sounds 

 and impulse of the heart are both perceived beyond the prsecordial 

 region, they give notice (generally speaking) of dilatation of one or 

 other of the ventricles. If, under these circumstances, sound pre- 

 dominates over impulse, then with dilatation there is either attenua- 

 tion, or somewhat less than a proportionate increase of its muscular 

 substance. If impulse predominate over sound, with dilatation, 

 there is either hypertrophy, or somewhat more than a proportionate 

 increase of its muscular substance." 



, * Lectures on Diseases of the Heart, vol. i. p. 18. 



