SECT. VIII. PHYSIOLOGY. 79 
SECTION VIII. 
Vascular Irritability. 
Motus, circulatorius non est vita, sed tantum instrumentum 
vite.—STAHL. 
cLxxxiv. Under the head of vascular irrita- 
bility, I shall comprehend the motion of the 
- heart, veins, arteries, and absorbents; and the 
expansion of these organs being nearly allied to 
muscular expansion, all that has been said on 
it, will bé applicable to the vascular system. A 
rigid adherence to anatomical connexion, would 
have brought the irritability of the heart under 
Visceral Irritability; but the functions of the 
vascular system, and the motion of the heart, are 
so immediately related, that it is impossible to 
consider them separately. The vascular system is 
a vast collection of tubes, varying in diameter 
according to the state of the vital force; and all of 
them are connected with the heart, through the 
medium of the great trunks from which they 
branch off, or in which they terminate. The 
heart thus forms a sort of central point in the 
