184 REPORT—1840. 
OssERVATIONS V. AND VI. 
July 1st, 1840.—In two observations, one on a Frog and a 
second on a Rabbit, the following results were obtained :— 
Rhythm: The first contraction after the pause or cardiac 
diastole was observed in the vena cava, to which immediately 
succeeded contraction of the sinus, and afterwards, immedi- 
ately, of the appendix of the auricles ; to which latter, imme- 
diately succeeded the ventricular systole; and the diastole, or 
relaxation of each part, succeeded in like order,—that of the 
vein first; then of the auricle, of which the appendix seemed 
later in its diastole than the sinus or body; then of the ven- 
tricles. Those motions were much slower than in the human 
subject—somewhere about fifty beats per minute. The series 
of systoles above mentioned succeeded each other, so that at 
a little distance they appeared collectively like an undulation 
commencing at the cava, rather than a series of independent 
actions.—Systole of ventricle: In diastole the ventricle was 
round, full, protuberant, and dark in colour; but on the 
supervention of systole changed rapidly in shape and colour, 
from purple, becoming pale flesh colour, like veal; and from 
round and broad, becoming apparently narrower and more 
conical and depressed ; being obviously lessened in all dimen- 
sions, but most strikingly in the transverse. The action of 
the heart lasted for.an hour or more with great regularity ; 
the auricles acted for some time longer than the ventricle, 
especially the right auricle. 
OsservatTion VI. 
In the rabbit, the heart did not beat at any time very 
vigorously or regularly, and ceased altogether after 20 to 25 
minutes, although respiration was maintained by the bellows 
with ease. 
The Rhythm: §.1. The first motion after the Pause or 
ventricular diastole was observed in the base of the auricles, 
and on the right side in the expansion of the jugular and sub- 
clavian veins, which in the rabbit, as Steno has noted, seemed 
to replace the superior cava. This vessel, whose dimensions 
were very large compared with the heart, and which wound 
round the root of the heart in its way to the auricle from above 
downwards, and from left to right, continued to pulsate for 
some time after the ventricles had ceased, and even after the 
adjoining auricle had been for some minutes inert. Nearly, 
but not quite, at the same instant of time with the vein, the base 
and then the apex of the auricle were seen to contract; after 
which (but not so quickly as might have been expected from 
