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versally believed; and though a mola has sometimes been found in 

 the uterus totally destitute of heart, and in which the blood must 

 have circulated, in its usual course, through the arteries and veins, it 

 cannot be known that there was any alternate pulsation ; and, even 

 if there was any pulsation, it must have arisen from preternatural 

 power in the arteries, and the resistance in the extreme vessels must 

 have been preternaturally small. 



The service which the author imagines is performed by the mus- 

 cular coats of arteries, is that of adapting their capacities to the va- 

 rying quantity of the blood contained in them. 



According to this statement, the qualities of the pulse, as discernible 

 to the touch, are ascribed almost entirely to the action of the heart. 



The duration from the natural state may consist either in a change 

 of the heart or of the capacity of the smaller arteries. The quantity 

 of blood transmitted may also remain the same, or be diminished, 

 or be increased. When it remains the same, the change cannot be 

 very material, and is not likely to lead to any disease of the vital 

 functions. When the quantity transmitted is smaller than in health, 

 the arteries must become contracted, and the veins distended. The 

 pulse must be small and weak, until the blood accumulated in the 

 veins stimulates the heart to greater action. From the vigour ac- 

 quired during the former remission of its exertion, the pulse becomes 

 full and strong, a greater quantity of blood being transmitted than 

 in health, as seems to occur in the hot fit of fevers. 



A relaxation of the extreme arteries may, at the same time, suffer 

 the blood to pass more easily into the veins ; but such a relaxation 

 may be carried to excess, and the arteries be thereby emptied ; so 

 that the pulse becomes small and weak, and the heart exhausted by 

 fruitless efforts to restore the equilibrium, as appears to occur in 

 typhus. 



As general derangements of the circulation appear to be concerned 

 in different kinds of fever, so partial ones have a similar relation to 

 local inflammations. The most obvious changes arise from partial 

 dilatations or contractions of the capillary arteries. Distension will be 

 accompanied with redness, pain, and heat. But it is possible that 

 another species of inflammation may also arise from an obstruction of 

 the extreme capillary arteries ; so that the small branches are sub- 

 jected to a pressure many times greater than that which they are in- 

 tended to withstand in their natural state, and the consequent dis- 

 tension will be accompanied with redness and pain. 



Besides these general illustrations of the nature of fevers and in- 

 flammations, the author is of opinion that the same theory may 

 be of use in explaining the operation of remedies employed for re- 

 lieving them, more especially (in the different modes of letting 

 blood), the more speedy and effectual relief from opening an artery 

 than a vein, and the great benefit often derived from the more prac 

 ticable expedient of withdrawing a small quantity of blood from the 

 immediate neighbourhood of the part affected, by cupping or by 

 leeches. 



