206 ON THE NATURE AND PRINCIPLES OF 



mainly depend upon the activity of the circulation 

 at the time of performing the experiment; but it is 

 here interesting to inquire, how an increased How of 

 blood into a particular artery causes an unnatural 

 amount of lateral pressure of the capillary streams 

 supplied from that vessel. And an examination of 

 this point is the more necessary, as it involves the 

 solution of a pathological problem of some importance, 

 vi/. the modus operandi of determination of blood in 

 inducing inflammation. 



Whatever may be the action of its immediate 

 cause, the pathological condition characterising de- 

 termination of blood is undoubtedly an unnatural 

 accumulation of that fluid in, and consequent dis- 

 tension of the arteries of, a particular part or organ ; 

 the blood columns contained within the minute 

 porous capillaries of the affected part moving more 

 rapidly than usual, and being therefore fi'ee from 

 any material increase in their lateral or distending 

 pressure. And as the facts and arguments adduced 

 in the preceding part of this communication suffice, 

 I think, to prove that inflammation is essentially 

 constituted by an unnatural increase in the lateral 

 pressure of the columns of blood contained within 

 the thin permeable capillaries, the question may be 

 reduced to a simpler form, and we shall merely have 

 to inquire how a certain physical derangement of 

 the arterial circulation in a particular part or organ 

 i - niaMcd to produce a similar affection of the capil- 

 laries continuous with the distended arteries. 



The smaller arterial ramifications, in their healthy 

 >tate, oppose a constant resistance to the distending 



