164 ON THE NATURE AND PRINCIPLES OF 



experiments was almost invariably caused by the 

 local application of some irritating substance. Any 

 conclusions drawn from the unnatural phenomena 

 then witnessed are, therefore, in strict reasoning, 

 to be considered as illustrative of the action of only 

 one class of the exciting causes of inflammation, 

 viz. local sources of irritation. 



Moreover the parts selected for observation are, 

 from the very transparency which recommends them 

 to the microscopist, evidently possessed of but a 

 slight amount of vascularity, and consequently do 

 not, in their diseased condition, exhibit such marked 

 phenomena as would be presented by parts more 

 copiously supplied with blood. And in most of the 

 observations in question the irritant seems to have 

 been applied to a very minute portion of the tissue 

 under examination, apparently for the purpose of 

 limiting its action to a small number of vessels. 



Now, if we contrast these conditions with those 

 existing in the generality of the cases of inflamma- 

 tion which we are called upon to treat in man, any 

 inferences legitimately deducible from the observa- 

 tions in question must, I think, be considered as 

 calculated to throw but a very faint light on the 

 nature of those extensive and serious disorders of 

 the circulation which, occurring in the highly vas- 

 cular organs of the human body, produce such 

 striking and injurious effects ; for neither in their 

 extent, intensity, nor causation, do the disorders 

 thus artificially created correspond with the great 

 majority of cases of inflammation presented to tin 1 

 medical practitioner. 



