172 ON THE NATURE AND PHINC'IPLES OF 



before stated to arise 1st, directly, from an in- 

 creased lateral pressure of the blood contained within 

 the minute porous vessels of the part: and -udly, 

 indirectly, by diminished support to, or pressure on, 

 the exterior of those vessels. It is evident, there- 

 fore, that a successful plan of treatment must 

 embrace, and be based upon an observance of the 

 two opposite conditions to those just specified. We 

 accordingly, as the general principles of treatment 

 endeavour - 1st, to diminish the lateral pressure of 

 the blood contained in the minute vessels of the 

 inflamed part ; 2ndly, to increase the pressure acting 

 on the exterior of those vessels. 



The first point is attained by blood-letting, pur- 

 gatives, and all other evacuants ; by digitalis, col- 

 chicum, and other substances which possess the 

 power of reducing the heart's action; and, after 

 depletion in strong subjects, or primarily in asthenic 

 systems, by derivatives or counter-irritants. These 

 measures, with the exception of the last-mentioned 

 group, act by diminishing the general pressure of the 

 arterial blood in the system ; derivatives can of course 

 only indirectly reduce the pressure of the blood- 

 colunins in the inflamed part by diverting a larger 

 proportion of the arterial blood to other vessels. 



The measures which accomplish the second indi- 

 cation are, mechanical support, friction, cold, and 

 astringents. The removal of any sources of impedi- 

 ment to the return of blood from the part, and an 

 attention, where practicable, to its position, are 

 beneficial observances, which are of course in perfect 

 unison with the preceding therapeutic principles. 



