|]g ON THE FUNCTIONS OF THE HEAitT AJJD ARTERIES. 



heart is smaller than in health, the arteries must be con- 

 tracted, until their tension becomes only adequate to propel 

 the blood, through the capillary vessels, with a proportion- 

 ally smaller velocity, and the veins must of course become 

 distended, unless the muscular coats of the arteries can be 

 sufficiently relaxed to afford a diminished tension, which is 

 probably possible in a very limited degree only. In this 

 state the pulse must be small and weak, and the arteries 

 being partly exhausted, there will probably be a paleness 

 and chilliness of the extremities: until the blood, which is 

 accumulated in the veins, has sufficient power to urge the 

 heart to a greater action, and perhaps, from the vigour 

 which it may have acquired during the remission of its ex- 

 ertions, even to a morbid excess of activity. Hence a con- 

 trary state may arise, in which the quantity of blood trans- 

 mitted by the heart is greater tbau in perfect health : the 

 pulse will then be full and strong, the arteries being dis- 

 tended, so as to be capable of exerting a pressure sufficient 

 to maintain an increased velocity, and to overcome the con- 

 Hot fit of feter. sequent increase of resistance; a state which perhaps con- 

 stitutes the hot fit of fever; and which is probably some- 

 times removed in consequence of a relaxation of the extreme 

 arteries, which suffer the superfluous blood to pass more 

 easily into the veins. Such a relaxation, when carried to a 

 morbid extent, may also be a principal cause of another 

 general derangement of the circulation, the motion of the 

 blood being accelerated, and the arteries emptied, so that 

 the pulse may be small and weak, while the veins are over- 

 charged, and the heart exhausted by violent and fruitless 

 efforts to restore the equilibrium ; and this state appears to 

 Typhus. resemble, in many respects, the affections observed in ty- 



phus. When, on the contrary, the capillary vessels are 

 contracted, the arteries are again distended, although with- 

 out the excess of heat which must attend their distension 

 from an increased action of the heart, and possibly without 

 Efftct of cold, fever: an instance of this appears to be exhibited in the 

 shrinking of the skin, which is frequently observable from 

 the tffect of cold, and in the tirst impression produced by 

 Cold fit of fe« a cold bath: nor is it impossible, that such a contraction 

 ^^'' may exist in the cold tit of an intermittent, although it seems 



mor©^ 



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