. 
the cheft, and affording, by its contractions, 
AY Nee 
power by which the circulation of the blood is carrie on. 
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who have written on the circulation fince the time of Harvey, 
have defcribed it in the fame manner, dividing this fun@ion 
» the great, and 
ti parts the lefs or pulmonary 
circulations, of which the heart is the common centre. 
; jeéts of the blood’s mo- 
tion through our organs ; I deem the mode, in which I 
1 parts 
The firft of thefe is” 
Jal t ungs 
: a oe of red blood, the ficond that of black 
ood. : 
Huid in its black ftate. From thefe capillaies it paffes 
e branches an 
d trunks of the pulmo- 
rterial fyitem. at- 
capillary fyftem (the capil- 
cepting thofe of the lungs), 
ogee as the termination of its courfe. 
haracters : here, if we may ufe the expreffion, 
t teems_ to be reproduced, ‘probably by the fubtraction of 
thofe Principles, which it had previoutly derived from t! 
hee "here in the lungs, Prom the seseral capillary fyftem 
the into the veins, ch bring it to the right cavities of 
artery heart : thence it is tranfmitted through the pulmonary 
trie. to the capillary fyftem of the lungs. The latter is its 
rps termination, as it is the commencement of the fyftem 
and feretghout, lines the whole paffage of the black blood, 
: for it an unbroken can along which it is con- 
Vou. XVII, 
r 
the chief ftantly conveyed from all parts of ep | to the lungs, 
fibrous tiffue in the pulmonary artery: but the membrane, 
as inthe preceding cafe, remains always nearly uniform, in 
ties ; as the membrane of the other circulation concurs in 
Differences of the twe Circulations: ~The general idea, which 
I have thus g 
in their motion. . There are in truth two hearts, a right and a 
left :-they might probably perform their fanGtions juit as well, 
if they were feparated, as in their prefent conneéted form, | 
Even when t oramen ovale remains open after birth, we 
r > 
all intermixtur: of the red and black blocds, and confequently 
the two Ree are flill equally independent, as far as fg 
e 
of the blood. ‘This complete feparation © 
that in which it is re- 
prefented as divided into the great and lefs, which are mani- 
feftly confufed and identified with each other. 
ccording to the obfervations already made, the two cir- 
culations begin and terminate in two capillary fyftems, which 
may therefore be confidcred as fi rming the limits’ within 
the other organs, with the fmall exception of the parts from 
which the blood of the 
each capillary fyftem is at once origin and termination: the 
‘pulmonary is the origin of the circulation of red ; and the 
and conclufion of the circulations, but it undergoes alfo a 
complete change-in its nature ; and in this refpeét the pulmo- 
nary and general capillary fyflems are the feat of the two 
moit important phenomena of the animal economy, viz. the 
— of the blood from black to red, and vice verfa.. Each 
ire 
ci tion evidently prefents three objets for our examina- 
tion; rift, the origin ; 2dly, the courfe; fl * “yp oe 
or thele the me- 
of each kind of blood. In the firft an 
ead 
be} ;; 
oc 
maffes, and, tee meet: 
fyftem, again dividing into fma 
the tilack blood, 
