HEART. 
the three eee arifing. sg its arch and the trunk after 
their ori garniie als : 60 
3789 to 46593 and 1521 es 2250, He fo 
tion of ae trunk of the fuperior mefenteric to its eleven 
branches to be as 529 to. 988: and of the carotid to its ex- 
ternal and internal branches as 529 to 768. 
Althotigh there can be no doubt that the capacity of the 
arterial fy le increafes as it proceeds from the heart, the 
general opinions co the mode and degree of this 
augmentation, and the ratio of the branches to the trunk in 
each particular inflance, have been called in ses by fome 
hyfiologifts. “ Ithas been commonly taught, “fays Blumen- 
es h,” that in the whole arterial fyftem, the branches are 
more ig th than the'trunk from which they arife. Ia 
prehend that this propofition has a enunciated too gene- 
rally, ‘and that the meafure of the diameter has heen often very 
improperly se saa with that of the area of the veffel. 
have examined t oint more than once, not in veffels 
diftended with injeGtion, But in ‘the undilturbed arteries of 
the moft recent fubje&s, and have found, in the cafe of the 
innominata and its right carotid A fubclavian branches, and 
of the brachial with 1 d-ulnar divifions, that the 
a exceed that of the trunk 
Py feet. 7, § 90.) Bichat men- 
i is fubject 5 « that of mea- 
is greater, in propor 
. thicknefs of their fides, te that of the Pr creed taken fe- 
parately : in other words, the parietes of the aorta are lefs . 
thick, ceteris paribus, in proportion to its cavity than thofe 
To this circumftance we may undoubt- 
edly refer the comparatively rare occurrence ef aneurifms in 
the branches, = their ra sare! in the trunks.’? Anat. 
and the arteries 
end: ‘idneds ftate, that it is at aie poi where the 
blood. aera he ae eneaely under the influence of the heart, 
and has its motion kept up by the infenfible contrattility of 
the vafcular parietes: but ~ fa 1e of demarcation cannot 
“be = obvious to re = 
: Y 
their ori ta tha our account of the capillary re . which is is 
through all the o 
dif “i 
cous, the cutaneous, the mufeular, 
fe 
Ou receive but w arteries, as the offeous, 
fibrous, fer if and have tk eref t b 
bs blood circulating through their capillaries. Laitly a the 
differing in their organization and appearance. The 
Geet thefe is pescly 1 the a ellular or external coat, and forms 
ome 
ess Within the Serer tie fcetat, the Si 
day a is covered i the refle SS them- 
brane, a certain quantity of cellular and adipous fh ubjfance 
being interpofed. On the left fide of the cheit, and in fome 
the abdomen, this artery and its iliac branches are 
peritoneum on their an- 
them to the ames ifcard, membranes, ca eed 
and mufcles. ‘The threads compofing it are fhort, and more 
0 
threads, united at very acute snitch. a nearly parallel, 
om bis rh and fometimes ceed the hike Joeath of 6334 
ves and finall. ls are frequently dif- 
per ed in thet fheaths, fo as £6 ‘ie a a peculiar reddifle | 
appearan remarkable se of this ftrudture may 
be feen in i the carotid artery. e thefe veffels are tor- 
yed ty tesa the cellar 
a 
outfides of the artery, more 
flated, or if its cells have been “tifte nded te maceration in 
‘water; hence it hea! of villous coat, as applied to the 
covering in que 
Immediately ieee the artery the cellular soins forms 
a very denfe, ome and firm layer, which on the firft view 
appears to be a peculiar membrane, but, on oie accurate 
examination, is i Bead to belong to the cellular f nie ts 
this is never the feat nf ferous “effufion in Saieara: nor does 
it ever contain fat. is formed by, 
tion oy the arid cellular bis which aflumes a 
more and arg co act texture, and the threads of which: 
are ‘te laft 
coniiderable maceration, the ¢ 
1 
“peas pro- 
coverings of the 
i 
arterial tubes ; and 2epay in 
on aneurifm, aa the two rsa, which we 
def 
i Chraedhis oF AES. is ; 
ed ee! fome es fimply ns 
ay 
fecond covering, ¢ 
dual tte. é 
