SECT. X. PHYSIOLOGY. : 93 
other hand, that the quantity of the blood which 
they contain, is dependant on their vital expan- 
sibility. I shall endeavour to demonstrate this 
allegation by analysis, by + gai tenet and ee ex- 
perimental facts. 
‘ccxiv. In the cold stage of an ague, when the 
vital force is low, the pulse is feeble; but in the 
hot stage, when the vital force is restored, the 
expansibility of the arteries, and the strength of 
the pulse, are augmented. The same series of 
phenomena arise from extremes of cold or heat. 
The extreme arteries are always morbidly ex- 
panded in local inflammation; but by reducing 
the vitality of the part, either by bleeding or 
topical application of cold, the arteries usually 
lessen in size, as the vital force decreases. 
ccxv. In whatever part of the body the animal 
temperature is lower than natural, there also the 
pulsation and expansibility of the arteries are 
lower than natural; and if the animal heat be 
locally or generally augmented, so also will be 
the expansibility of the arteries. 
ccxvi. That the contraction of the heart is 
not the cause of arterial expansion in the above 
instances, may be established by experiment. 
When the vital force of a paralytic arm is raised, 
by applying nitrate of silver in the axilla, the 
natural expansion of the brachial artery is 
