PRACTICE OF PHYSIC. 



DCCXLV. This reasoning will, in some measure, explain 

 the production of haemorrhagy. But it appears to me, that, 

 in most cases, there are some other circumstances that concur 

 to produce it : for it is probable, that in consequence of conges- 

 tion, a sense of resistance arises and excites the action of the 

 Vis Medicatrix Naturae ; the exertions of which are usually 

 made by the formation of a cold stage of pyrexia, inducing a 

 more vigorous action of the vessels ; and the concurrence of 

 this exertion more effectually opens the extremities, and occa- 

 sions the flowing out of the blood. 



"Active haemorrhagy depends on an increased impetus of the 

 fluids, which is always founded upon a pyrexia; but the founda- 

 tion of this pyrexia is a previous congestion, from which it ap- 

 pears, that this congestion is the source of all the phenomena. 11 



DCCXLVI. What has been delivered in the two preceding 

 paragraphs, seems to explain the whole phenomena of haemorr- 

 hagy, except the circumstance of its frequent recurrence, which 

 I apprehend may be explained in the following manner. The 

 congestion and consequent irritation being taken off by the flow- 

 ing of the blood, this, therefore, soon after, spontaneously 

 ceases ; but, at the same time, the internal causes which had 

 before produced the unequal distribution of the blood, common- 

 ly remain, and must now operate the more readily, as the over- 

 stretched and relaxed vessels of the part will more easily admit 

 of a congestion of blood in them, and, consequently, produce 

 the same series of phenomena as before. 



DCCXLVII. This may sufficiently explain the ordinary re- 

 turn of haemorrhagy ; but there is still another circumstance, 

 which, as commonly concurring, is to be taken notice of; and 

 that is, the general plethoric state of the system, which renders 

 every cause of unequal distribution of more considerable effect. 

 Though haemorrhagy may often depend upon the state of the 

 vessels of a particular part being favourable to a congestion's 

 being formed in them ; yet, in order to that state's producing its 

 effect, it is necessary that the whole system should be at least in 

 its natural plethoric condition ; and, if this should be in any de- 

 gree increased beyond what is natural, it will still more certain- 

 ly determine the effects of topical conformation to take place. 

 The return of haemorrhagy, therefore, will be more certainly oc- 



