TEEATMENT OF INFLAMMATION. 187 



an unequal distribution of the blood, and consists 

 in the accumulation of an unnatural quantity of that 

 Jluid in the arteries of a particular part the capil- 

 laries or minute porous vessels being comparatively 

 unaffected. In their essential nature, and in the 

 operation of their causes, determination and inflam- 

 mation are very similar ; the chief difference be- 

 tween them being constituted by the pathological 

 phenomena which they respectively occasion. And 

 this variety in their effects is a natural consequence 

 of the different physical properties possessed by the 

 affected vessels. For the thin membrane forming 

 the parietes of the capillaries readily admits of the 

 exudation of liquor sanguinis when in a state of un- 

 natural compression, while the thickness and density 

 of the proper arterial tunics effectually prevent the 

 escape through them of any portion of the contained 

 blood. 



Before, however, considering the questions con- 

 nected with determination of blood, it is necessary to 

 refer to an analogous disorder of the circulation, of 

 which the aorta itself is occasionally the seat. And 

 the study of this physical peculiarity of the great 

 mass of arterial blood is the more interesting, as it 

 illustrates the operation of the causes producing a 

 similar condition of the blood contained within the 

 smaller vessels of the arterial system. 



In a former paper on the physiology of the circu- 

 lation, I pointed out the circumstances which influ- 

 ence the amount of lateral pressure exercised by the 

 mass of blood contained in the aorta, and further 

 observed, that " as this force is equally affected by 



