184 THE ACTION OF 



pain, we should first inquire why inflammation is 

 painful ; in what way do the vascular and other 

 changes that take place in inflamed areas irritate 

 nerve-endings ? It cannot be merely by the flushing 

 with blood, because Bier's bandage greatly increases 

 this, and yet relieves pain. It may be by the 

 chemical irritation produced by the toxins, or more 

 probably by stretching of nerve-endings owing to 

 the swelling up of the tissues with inflammatory 

 exudate. That stretching will cause acute pain is 

 shown by its occurrence in colic. Dropsy is not 

 painful, because in that condition the fluid passes 

 out passively where the resistance is least, as in 

 the subcutaneous tissues ; whereas inflammatory 

 exudation is an active process affecting all the tissues 

 involved in the inflammation, even when they are 

 tense and full of nerves. 



It seems strange to claim that vascular dilatation 

 should relieve such a condition. Would it not rather 

 add to the painful tension ? In unyielding structures 

 this may be true ; the general vasodilatation and 

 falling blood-pressure just as we go to sleep will 

 exaggerate the aching of chronic bone inflammation. 

 But we must consider how the painful exudation of 

 plasma into all the interstices of the tissues is to be 

 removed ; it can only be by increasing the lymph 

 flow, by increasing the absorption of fluid by the 

 venules, and by washing away the toxins which set 

 up the exudation. To increase the lymph flow, the 

 part must be elevated and a better " head " of water 

 provided by vasodilatation. To increase absorption 

 by the blood-stream, there must be vasodilatation. 



