TREATMENT OF INFLAMMATION. 191 



that fluid in the large arterial trunks. The experi- 

 ments of Poiseuille, moreover, show that under such 

 circumstances the heart exercises a compensating 

 power, increasing the force of its contractions so 

 much as to raise the pressure of the aortic blood 

 considerably above its natural amount. In some 

 instances, where the bent tube was applied to the 

 carotid after ligature of the aorta, the mercury indi- 

 cated a pressure double the amount of that which 

 had been previously observed. And the effect of 

 the temporary obliteration of a great number of 

 minute vessels upon the condition of the aortic blood 

 is precisely similar, though of course less intense in 

 degree. 



In whatever manner produced, this unnatural 

 amount of pressure of the aortic blood, acting equally 

 in every direction, may occasion morbid effects, from 

 its distending influence upon the coats of the aorta ; 

 or it may affect the heart from its backward pressure ; 

 or it may cause the accumulation of an unnatural 

 quantity of blood in the smaller arteries of the body. 

 Each of these effects is worthy of a brief considera- 

 tion, and the third is particularly interesting, from 

 its presenting, on a more extended scale, those phe- 

 nomena which, when confined to the arteries of a 

 particular part or organ, constitute determination of 

 blood. 



The thick elastic walls of the aorta are, in their 

 healthy state, so admirably adapted to the peculiar 

 position of that vessel in the circulating apparatus, 

 that their rupture under the distending pressure of 

 the contained blood is never witnessed but as the 



