of opinion, as others say the vessels dilate first. That contraction of 

 the blood vessels, is the first process is well exemplified, when the end 

 of a finger is suddenly snapped off by machinery, or a gash is quickly 

 made in the flesh, for then the neigbouring parts become perfectly pale, 

 and no blood is seen for a few moments, owing to the sudden contraction 

 of the vessels from the shock. Dilatation next takes place when the 

 blood flows freely. If the irritation, or cause, be not removed, the 

 blood vessels become distended, and, finally, paralyzed. The corpuscles 

 crowd into the part, and becoming adhesive — sticking together, as it 

 were — induce further expansion of the vessels. 



i6. Congestion next takes place with the exudation, or oozing, of 

 the fluid portions of the blood through the sides of the vessels into the 

 surrounding tissues ; or the vessels may ultimately give way with 

 extravasation of blood into the parts, and from the consequent pressure 

 the nerve filaments lose their controlling power, and the structure 

 becomes changed. That the minute tissues play an important part 

 in inflammation cannot be doubted, because the blood, before it 

 reaches, and after it leaves, the inflamed portion, is the same as that 

 in the uninflamed parts of the body. 



17. The noted external local signs of inflammation are Heat, Pain, 

 Redness, and Sivelling. 



18. Heat is caused by the large amount of blood sent to the affected 

 part, and the consequent increased chemical action that follows. The 

 heat is not, however, so great as is thought, for the temperature does 

 not increase more than two or three degrees ; and yet in an inflamed 

 foot there is a perceptible increase of heat. We can, however, have 

 heat without inflammation, as the body often becomes heated from 

 exercise or hard work. 



ig. Pain is owing to the irritation of nerve fibres, from the pressure 

 caused by the distension of the effused blood materials. Pain, 

 however, varies in different portions of the body ; it may be reflex and 

 far distant from the affected part ; in some places it is dull, as when 

 the mucous membranes are inflamed ; but when fibro-serous or serous 



