The (His TO-R WW 
themfélves in the bones of the fkull. The ar- 
teries of the vertebra, alfo arife // from thefe 
branches ; and at length uniting together by 
a manifeftly confpicuous anaftomofis, they con- 
ftitute the trunk of the loins; out of which 
rifes the celiac artery, which afterwards fends 
out from it m, the mefenteric artery. Some ar- 
teries alfo, as thofe of the loins 27, and thofe 
that are detached to the tefticles, ovary 00 and 
reins p, have their origin from the fame trunk ; 
and this fame trunk is itfelf afterwards divided 
in the laft place into the iliac gg branches. 
The blood being driven out of the heart 
through all thefe arteries, to the circumference 
of the body and vifcera, at laft returns by a 
manifeft circulation through the veins to the 
heart, as to its center; whilft in the mean time 
only a part of it circulates through the lungs, 
and indeed exactly in the fame manner in 
which it circulates through the mufcles and 
the reft of the vifcera. ‘Therefore, the blood 
in the Frog circulates in a quite different order, 
than is obferved in other animal quadrupedes, 
or in fifhes ; in which all the blood paffes 
either thro’ the lungs, or thro’ the gills: that 
is, the upper trunks of the vena cava, which 
are united to the auricle of the heart, and are 
here delineated under both trunks of the great 
artery, do not in the Frog deduce their blood 
from the lungs; but they imbibe it directly 
from thefe veins, which run in the upper part 
of the body, and from fome others that are 
fituated next to the fkin in the fides lower 
down, and they likewife get a {mall portion, 
that returns from nourifhing the lungs. The 
blood, on its return from the lower parts of 
the body, does not touch the lungs, but dif- 
charges itfelf thro’ the porta and cava, into the 
auricle of the heart, without coming near the 
lungs.. Therefore, by inflating only one vein 
of the Frog’s body, the arteries may be all in- 
flated alfo. eit 
The diftribution of the Veins differs here 
confiderably from that of the arteries; for 
the two trunks of the the cava, are confpicuous 
above at the auricle, Tab. XLIX. Fig. tv. aa, 
where I have opened 4, the arteries, emit pul- 
monary veins out of their lower fide, (here cut 
off ) cc, which are twice as large as the arte- 
ries. . Thefe veins are properly placed in the 
cavity of the lungs, and particularly in the ex- 
tremities of the pulmonary veficles, and in the 
loins ; and they diffufe their capillary, and al- 
moft inviftble branches all over the cells ; nay, 
even thro’ the coat which invefts them. Here, 
therefore, in the lungs of the Frog, a confi~ 
fiderable blood-veffel, namely, the arterial vein, 
is wanting: the animal has no need of this ar- 
tificial canal ; fince Nature did not intend that 
all the blood fhould pafs thro’ the lungs. _ Be- 
fides, the two upper trunks of the caya pafs 
above the arteries in the Frog, and are alfo di- 
vided into various branches. Some little veins 
are from thence detached 4d, to the parts about 
the mouth : others, which bend very beauti- 
fully in their paflage, go towards the head ee, 
and give a part of themfelves /f, to the mufcles 
of the firft pair of legs. The axillary veins 
‘oe. J NYSOESG oIS. iat 
alfo, {pring gg, from the fame trunks, and 
emit two very confiderable 44 branches, which 
in the ilia beautifully bend themfelves back 
under the {kin above the mufcles of the belly ; 
and from thence afcending again towards the 
thorax, and being there confiderably dilated, 
they communicate, by a mutual anaftomofis, 
with the reft of the veins that are fituated about 
thefe places. The trunk of the cava, which 
is fituated beneath the heart, is fimple z, and is 
there divided into three branches, which are 
difperfed thro’ £2 the liver. A little lower, the 
mefenteric vein rifes / out of the liver:. under 
which the trunk of the cava very beautifully dif- 
fufes m itfelf, by many branches over the kid- 
neys; and at length, after dividing into two 
parts, conftitutes the iliac 2 2 branches, from 
which the epigaftric vein is obferved to rife 00 
very beautifully. This vein goes back along the 
ftraight mufcles into the liver; where I repre- 
fent it cut off. But if this little veffel, and all 
‘the intecuments of the belly, be diffected neat 
the liver, and then turned above the hind legs ; 
all the veins of the body may be conveniently 
inflated through it. By this means veins are 
difcovered in the liver, the kidneys, and all the 
vifcera.. And from thence I took an oppor- 
tunity of making, with very little labour, the 
following very remarkable experiments. Let 
what hath been hitherto faid, fuffice in regard 
to the circulation of the blood, and the blood- 
veffels in the Frog. 
Having finithed the obfervations now re- 
cited, as quick as poffible, I afterwards ex- 
amined fome mufcles, and alfo the fkin, eyes, 
and blood of a full-grown Frog. I found it 
eafy to divide the moving fibres of the mutcles 
fo {mall, that they refembled a Spider's web. 
But when I put them divided in this manner 
under the microfcope, I found they confifted 
of {till {maller fibres, and thofe of very minute 
globules. I firft difcovered the epidermis in the 
{kin ; it fupported the real ikin, the latter be- 
ing adorned with beautiful colours and black 
{pots, and appearing compofed, as it were, of 
lobules. I further feparated the {kin into a 
glandular fubftance, which was compofed of 
very numerous globular glandules. Thofe glan- 
dules fecreted that vifcous or flimy matter, 
which is obferved to be {pread over the furface 
of the Frog’s fkin, and rendered the latter very 
{mooth and flippery. ‘This {pecies of mucous 
matter taftes bitter, and offends the eyes with 
its acrimony ; nay, it caufes a fenfible pain, if 
rubbed to our fkin when wounded a little; fo 
that we muft be cautious in the ule of it, f 
next examined the aqueous humour of the eye 
ina glafs tube; but I perceived nothing more 
than the clearnefs of the liquor. And hence, 
then putting both extremities of that tube to a 
Jamp, I boiled that and the whole Frog's eye in 
water: but there were no globules con{picuous 
in it from this procefs. Both the white part 
of the cryftalline humour, which refembles 
chalk, and furrounds it, and the other &brous 
diaphanous portion, which is divided into feveral 
lamellz or plates, confifted entirely of globules, 
I faw a ferum in the blood, in which were 
Hh a vatt 
