206 REPORT—1840. 
phragm, excepting in its shape and size, and in the thickness 
and tension of its parietes, and the capacities of its cavities. 
The doctrine, that the precordial pulsation is caused by a blow 
received by the ribs, in consequence of the heart’s “jumping” 
(ada, Hippocrates) or “striking” against them (‘ pectus ferit,” 
Harvey; ‘‘ costam ictu percutit,” Haller, &c. &c.), appears to 
be superfluous, with a view to explanation of phenomena 
(notwithstanding the ingenious illustrations of the ancient opi- 
nion by Senac and Hunter), and to be substantially unfounded 
in point of fact. 
8th. That the arterial diastole or pulse, almost everywhere 
outside of the pericardium, perceptibly succeeds to the cardiac 
systole ; though near the heart, the interval between them is 
very brief, and to unpractised observers difficult to distin- 
guish. 
Sounds. 
9th. That the first sound of the heart depends partly, but 
in a slight degree, on the abrupt closure and transitory ten- 
sion of the auri-ventricular valves, which give to this sound its 
sharp, well-defined beginning; but that the first sound is 
mainly attributable to cardiac muscular tension alone, and that 
its prolonged duration is probably owing to the progressive 
character of the normal systolic effort from fundus to apex; 
and that this sound is probably, in no degree or condition, 
attributable to any blow or stroke of the heart against the 
ribs. 
10th. That the auricular systole is attended by an intrinsic 
sound resembling that of the ventricles, but more short, ob- 
tuse, and feeble. ‘This auricular systolic sound is often diffi- 
cult of detection, even on the naked heart, and with tolerably 
vigorous action of the auricles, owing to its being, to the inex- 
perienced ear, absorbed in, or masked by, the immediately- 
succeeding and vastly louder systolic ventricular sound. 
11th. That the sounds of friction in pericarditis may, where 
well marked and under ordinary circumstances, be expected 
to be double at least, and they may be, not improbably, triple 
or more. In its systole, each cavity of the heart moves so as 
to cause a friction, in one direction, of its attached lamina 
against the adjacent free lamina of the pericardium; and in 
its diastole, a pericardial friction is caused by each cavity in 
an opposite direction; and as the auricles move to and fro in- 
dependently of the ventricles, the normal pericardial frictions 
must be quadruple, or double with the auricles and double 
with the ventricles. If, therefore, those frictions were ren- 
