HEART. 
whether any fympathetic phenomenon takes place in the vein 
large trunks of the cave, fubclavian,. &c. be- 
caufe they are commonly diftended at the moment of death, 
fo as to appear much larger than is natural to them: it is in 
the branches and fmaller {ubdivifions that we find the difpro- 
portion allu Yet the right fide of the heart does not 
aller proportional fize of the 
veins, at the period alluded to, arifes le the rapidity of 
nutrition, which difpofes of much matter in the growth 
of the body, fo that there is lefs to be fent back i 
through the veins. i i 
time of birth, the 
which they exhibit in the adult. 
er, and are confequently more prominent. 
ftreng contractions of the 
mufcles of a limb in a youth and a full-gr vn man will thew 
this difference. BE wait 
In ol e veins become very large as compared with 
his point an inverfe difpofi 
PY he 
e 
t 
Th 
valet fancy, . 
The veins lower parts are more dilated in old a 
than thofe of the upper ; on account of the habitual rs 
yourable influence of the pofition of the - Since the 
peaggeie wee y | motion is comparatively weak in this fy{- 
tem, mechanical caufes have confiderab 
* 
tion ; hence the 
ve 
=) wellings, ' 
the. common complaint of old age, while aneurifms are rare : 
, 
the rupture of the veins, too, has commonly taken Place at 
is or the adult age, but'not in infants. : 
pulmonary artery of the old fubje& does not under. 
0 a dilatation analogous tothat of the veins, with which it 
Soca one fyftem. Removed from the operation of external 
agents, furnifhed at its commencement with a mufcular im- 
pelling organ, and formed of a firm and refifting tiflue, it is 
not expofed tothé caufes of dilatation. 
Two kinds of accidental developement of the yenous fyf. 
tem may be obferved: 1{t, in various tumours, which re- 
ceive a large quantity of venous blood, and from which there 
muft be a correfponding quantity of black blood returned. 
The enlarged fuperficial veins form a ftriking charaéter of 
j ” 
Dlesc5 
__ Remarks on the Pulmonary Veffels —The pulmonary artery, 
which is reprefented in the foregoing account as formitg — 
a 
defcribed to belong to that of the red blood, belong to thofe 
two fyems refpeétively, only inafmuch as they are lined 
by the common membranes, of which the nature is the fame 
throughout all parts of each fyftem. But the tiflue of the 
pulmonary artery, although added to the membrane of black 
ju th 
blood, is ju 
or 
1 
» 
fm] 
oO 
© 
i 
a] 
@ 
A. 
o 
— 
o 
2) 
& 
° 
4 
ms 
~~ 
c 
t=} 
Du 
a 
o 
n fun& 
of the circulation 
monary arte 
There are fome modifications dependent on local caufes ; 
thus, on account of the fhort courfe defcribed by the pul- 
lonary veins, gravity has no influence on their blood, and 
they never become varicous. pais 
e fame general difpofitions are obferved in the arteries 
e e 
mouths, as the motion of their fluid is ae uniform in | 
parts of their fyftem, but may experience local acceleration 
or retardment, : 
Abdominal Syftem of black Blood.—The abdomen contains 
a fyftem of vetfels, in which black blood circulates, ab 
lutely independent of the preceding, called the vena porta: - 
in mo imals, i 
digeftive apparatus, ‘this fyftem forms 
which are f{peedilv united into Le 
‘ain into an infinity of ramifications, which 
are loft in. the tiflue of the an Thus we have the fame 7 
x : ; minal portion o 
of this fyitem is performed in the Jame manner ane 
