122 



Tcntfency of 

 inflammation 

 to ei.tend it- 



Operation of 

 remedies for 

 inflammalion 

 and fevers. 



Topical vene- 

 section. 



OS THE FUNCTIONS OF THE HEART AIN^D ARTEItfES. 



Perhaps the capillary vessels are dilated, while the arteries, 

 which are a little larger only, are contracted : possibly to© 

 an obstruction may exist at the point of junction of the ar- 

 teries with the veins; ^ud where the blush is preceded by 

 paleness, such an obstruction is probably the principal cause 

 of the whole affection. 



With respect to the tendency of inflammation in general 

 to extend itself to the neighbouring parts, it is scarcely pos- 

 sible to form any reasonable conjecture, that can lead to its 

 explanation : this circumstance appears to be placed beyond 

 tlie reach of any mechanical theory, and to belong rather to 

 some mutual communication of the functions of the nervous 

 system ; since it is not inflammation only, that is thus pro- 

 pagated, but a variety of other local afTections of a specific 

 nature, which are usually complicated with inflammation, 

 although they may perhaps, in some cases, be independent 

 of it. Inflammations, however, are certainly capable of 

 great diversity in their nature, and it is not to be expected, 

 that any mechanical theory can do more than to afford «* 

 probable explanation of the most material cirqunastances, 

 which are common taall the different species. 



Beside these general illustrations of the nature of fevers 

 and inflammations, the theory which has been explained 

 may sometimes be of use, in enabling us to understand the 

 operation of the remedies employed for relieving them. 

 Thus it may be shown, that any diminution of the tension 

 of the arterial system must be propagated from the point at 

 which it begins, as from a centre, nearly in the same man- 

 ner, and with the same velocity, as an increase of tension, 

 or a pulsation of any kind would be propagated. Hence 

 the effect of venesection must be not only more rapidly, but 

 also more powerfully felt in a neighbouring than in a dis- 

 tant part: and although the mean or permanent tension of 

 the vessels of any part must be tke same, from whatever 

 vein the blood may have been drawn, provided that they 

 undergo no local alteration, yet the temporary change, pro« 

 duced by opening a vein in their neighbourhood, may have 

 relieved them so effectually from an excess of pressure, as 

 to allow them to recover their natural tone, which they 

 could not have done without such a partial exhaustion of 



the 



