96 

 PART III. 



DISEASES OF THE HORSE. 



CHAP. XXI. 



ON INFLAMMATION. 



[Inflammation is usually considered as a disorder of the blood 

 vessels, but we can best understand its nature by considering the 

 phenomena with which it is connected. If, then, any external 

 part of the body present the symptoms of sivelling, redness, and 

 pain, we may justly consider it in a state of inflammation. The 

 swelling is to be attributed in the first place to the fulness of the 

 vessels of the parts, but after a while an effusion takes place from 

 the surfaces of these vessels, and thus keeps up or increases the 

 enlargement. The redness is owing partly to the greater quan- 

 tity of blood in the arteries of an inflamed part ; but principally 

 to the fact that the small capillary vessels, which in a state of 

 health may not contain red blood, are now enlarged, so as to 

 admit the red particles. The pain of an inflamed part is owing 

 to the pressure of the enlarged vessels on the nerves of sensation ; 

 but this symptom is not always present — only indeed where the 

 distension is sufficient to produce severe pressure, or where the 

 part is more largely furnished with nervous fibres. 



A part in a state of inflammation is therefore more abundantly 

 supplied with blood than in a state of health, and after a time 

 the vessels themselves become enlarged, and in many cases new 

 vessels are formed in a short space of time ; as was proved by the 

 celebrated Mr. Hunter, who caused the ear of a rabbit to freeze, 

 and then suddenly thawed it, and thus produced great inflam- 

 mation, when it was found that the ordinary vessels were en- 

 larged, new ones formed, and the substance of the ear thickened. 



The capillary vessels in an inflamed part become distended 

 often beyond the power of contraction, and are partially ob- 

 structed, which may be noticed when the conjunctiva of the eye 

 is inflamed ; vessels which were not perceptible become visible, 

 and are loaded with red blood, which they did not contain 

 before. And after the inflammatory action has subsided, many 

 of the small vessels continue for some time full of red blood, 

 from being in a state of debility, and unable to contract on their 

 contents, which they are assisted in doing by the use of external 

 stimulants. 



