HEART. 
‘openin gs 
the aort: 
communication of the pu 
i H 
ti aorta has arife the right ventricle, and 
the onary artery from the left. In fome of the 
cafes $ arteriofus is more pervious 
duration of their lives feldom extends beyond a few months ; 
but it may be protracted to fome years where the malforma- 
tion allows a confiderable portion of red blood to be cir- 
culated in the body. See the Medical Obfervations and 
Inquiries, vol. vi..; Medical Vranfa@tions, vol. iii. ; Sandi- 
fort's Obfervationes Anatomice ; and Dr. Baillie’s Morbid 
tomy. ; 
On the fubje& of the properties of the heart, we muft 
refer the reader to the general account of the organic muf- 
cle the article Muscie. We have a few remarks only 
to make here, 
n the ri 
the body. 
_ Varieties 
by the blood 
- Hence, in of the heart 
-which the difeafed bulk can be com . This phenomenon, 
which arifes merely from the extenfion of the undifeafed car- 
diac cavities, muft not be confounded with the aneurifmatic 
. of the heart fide of the vifcus often 
. 
a 
ne magia heart is 
unctured, the efcape of the contai uid is followed b 
a reduction of fize ; but the aneurifmatic heart does ttf 
regain its natural 10us on the evacuation of its con. 
tents, 
The contrattility of the heart mikes it contraét when the” 
when an animal dies 
* 
i, 
- figns of pain, 
é 
: L 
caufe of the heart’s dilatation, the admiffion of a 
dition of the organ is obferved; and there js every inter. 
mediate degree between thefe. 
That the heart does not poffefs animal fenfibility is obvious 
from the refult of experiments, in which animals do n 
of the 
o kinds: i 
tarily arrefted, and fyncope enfues, 
the impreffion of confiderable and fudd. 
our 
obitacle to the blood’s courfe, which excites the heart to 
increafed exertion in order to furmount it. Moreover, if — 
there fhould be no obftruction, but merely pain, and febri 
irritation {upervenes, the effeé&t mutt be fympathetic. That 
the increafed aGtion of the heart may depend on the admix- 
ture of a foreign fubftance with the blood, which renders it 
ATION we have mentioned, as the 
of blood into its cavities 3 on which fuppofition the organ aj 
owing ar- 
ements of Bichat render it doubtful whether this {uppofition 
altogether juft. Expofe the heart and empty it, if a ite 
ied, it will ftill contraét and dilate alternately 
piace. th rs P 
In the oppolite hand, you will then find that the effort of 
he heart is irritated with the pa 
of a knife it ufually contraéts ; but fometimes it dilates firl, 
and contraéts fubfequently. 
derable 
* 
