L120 
The 2B Ot OR: for aN Ad UGR Cris ier; 
Of the circulation of the blood in a full-grown Frog. 
HE manner in which the blood circulates 
in the full-grown Frog, is not a point of 
{mall moment: indeed, it very much recom- 
mends comparative anatomy, fince, when that 
is not thoroughly known, it feems that one 
cannot arrive at the real knowledge of the ufe 
of the vifcera. The famous Malpighius, 
Needham, and many others, fay that the Frog 
has vifible lungs and refpiration. Nay, they 
alfo think that the blood circulates through the 
lungs, is there elaborated, leffened in the 
‘globules, and brought to its full perfection: 
and hence the office of fanguification, which, 
in former ages, was fuppofed to be done by 
the liver, is now transferred from thence to 
the lungs. Befides, fince the fame gentleman 
has obferved gills in Fifh anfwering the pur- 
pofe of lungs, thro’ which all the blood circu- 
lates ; and as they faw the water ftrike againft 
thefe in the manner as the air does again{ft and 
into the lungs, in other animals, they have 
therefore made the gills perform the office of 
making blood. 
I confefs, this opinion is very ingenious; if 
it be fuppofed, that the liver does in no wife 
contribute to make blood. But from whence 
fhall fanguification be derived in this animal, 
which has lungs; but at the fame time they are 
fo circumftanced, that the blood does not pafs 
thro’ them, but is immediately diftributed all 
over the whole body, out of the fingle ventri- 
cle which their heart hath, without touching 
the lungs? This plainly is the cafe in Frogs. 
The fame thing, probably, holds in Toads, 
Water-newts, Lizards, Chameleons, Tortoifes, 
Serpents, and other creatures of that kind ; 
all which I have obferved to be provided with 
membranaceous lungs: tho’ I have not yet 
accurately examined their blood-veflels. We 
thali certainly be obliged to return to the liver, 
and reftore it to its former degree of dignity. 
Nay, this holds more ftrongly in the Frog, 
which is deftitute of the lacteal veins: fince 
its chyle muft, for that reafon, neceflarily en- 
ter the great numbers of its meferaic veins, and 
be thus conveyed thro’ the vena porta to the 
liver. In the extremity of this vein, the blood, 
which is to pafs from thence into the cava, is 
broken and divided; and it feems to me to 
acquire its laft perfection in the cava itfelf. 
As, I am confident, I fhall, at fome time, more 
fully demonftrate, with refpect to thofe ani- 
mals, which have lacteal veins. But I cannot 
now, for want of time, finifh the experiments, 
which I have began, concerning this fubject : 
and which, tho’ not many in number, are yet 
fo important, as to promife great difcoveries. 
Having premifed thefe things, 1 fhall now 
briefly defcribe the principal arteries and veins 
in the Frog, and fhall thew the manner in 
which the blood circulates thro’ them. The 
Frog’s heart, Tab. XLIX. Fig. 111. 2, as is the 
cafe in moft Quadrupedes, is found fituated in 
2 
the cavity of the breaft, which is indeed very 
fmall. To the upper part of the heart, the 
auricle 4 is obferved to be joined: but it has, 
like the hearts of Fifth, only one ventricle, out 
of which likewife there iffues only one artery ; 
which is in the beginning confiderably mufcu- 
lar, and fufficiently dilated, and immediately 
afterwards dividing into two trunks; one of 
which is detached to the right region ¢, the other 
to the left region of the breaftd. Lach of thefe 
arteries, which are like the fubclavian veins, 1s 
further divided into three principal branches. 
The firft of thefe, which is the leaft ee, ftretches 
on each fide to the lungs, and gives them nou- 
rifament: and therefore I cajl thefe the pul- 
monary arteries, and they are of the nature of 
thofe called Bronchials in man and brutes. 
Thefe, in their courfe to the lungs, are com- 
monly divided into three branches, which [ 
here exhibit as cut off; and after this ftretching 
to the coat that furrounds the lungs, thereon 
form a very admirable piece of net-work, and 
communisate with each other by feveral ana- 
ftomofes: hence they alfo pafs down by very 
{mall fhoots, into the inward irregular veficles 
of the lungs, among which the pulmonary vein 
is diffufed, and with the latter they form a very 
confpicuous anaftomofis, vifible even to the 
naked eye. This is manifeft, if thefe veins 
and arteries be filled with quickfilver. I keep 
fome prepared in this manner. Out of the 
pulmonary arteries likewife proceed two {mall 
branches, Tab. XLIX. Fig. 111.7 on each fide, 
turning upwards, which are diftributed thro’ 
the parts of the mouth. 
The fecond pair of the principal branches, | 
arifing out of the trunk of the great artery, are 
obferved to be dilated into two remarkable 
{wollen knots; thefe are of a grayifh black co- 
lour gg, in the living Frog. Both thefe arte- 
ries are after this extenuated, and, together with 
the little branches iffuing from them, feem de- 
figned only to ferve the mufcles of the mouth, 
and thofe of refpiration. But as each of them 
afcends higher, it is again dilated into a knotty 
little bladder. I thould think thefe arteries are 
duplicates of the nature of thofe which before 
ferved for conveying the blood to the gills. 
This I cannot affirm for certain ; but it may be 
hereafter examined into by repeated diffections. 
The third pair of the primary branches are 
particularly worthy of confideration ;  fince 
thefe properly conftitute the trunk of the ar- 
teria magna in the region of the loins, and are 
there for that purpofe united by a very con{pi- 
cucus anaftomofis. They rife out of the trunk 
of the arteria magna, then they bend ¢ circu- 
larly under the lungs; and, after fending out 
fome branches, they likewife emit zz the axilla- 
ryarteries from off their fides. We obferve, that 
a little deeper beneath the heart, the carotid 
arteries arife from them; and that thefe afcend- 
ing && from thence towards the head, bury 
themfelves 
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