FUNDAMENTAL PRINCIPLES OP DISEASE. 33 



spavins, ringbones, inflammation of the glands of the less vascular 

 skin of the extremities, greasy heels, thrush, etc. 



Young horses have inflammation of the membranes lining the air 

 passages and digestive tract, while older animals are more subject to 

 troubles in the closed serous sacs and in the bones. 



The work to which a horse is put (saddle or harness, speed or 

 draft) wiU influence the predisposition of an animal to inflammatory 

 diseases. As in congestion, the functional activity of a part is an 

 important factor in localizing this form of disease. Given a group 

 of horses exposed to the same draft of cold air or other exciting 

 cause of inflammation, the one which has just been eating will be at- 

 tacked with an inflammation of the bowels; the one that has just 

 been working so as to increase its respiration will have an inflamma- 

 tion of the throat, bronchi, or lungs ; the one that has just been using 

 its feet excessively will have a founder or inflammation of the laminae 

 of the feet. 



The direct cause of inflammation is usually an irritant of some 

 form. This may be a pathogenic organism — a disease germ — or it 

 may be mechanical or chemical, external or internal. Cuts, bruises, 

 injuries of any kind, parasites, acids, blisters, heat, cold, secretions, 

 such as an excess of tears over the cheek or urine on the legs, all 

 cause inflammation by direct injury to the part. Strains or wrenches 

 of joints, ligaments, and tendons cause trouble by laceration of the 

 tissue. 



Inflammations of the internal organs are caused by irritants as 

 above, and by sudden cooling of the surface of the animal, which 

 drives the blood to that organ which at the moment is most actively 

 supplied with blood. This is called repercussion. A horse which 

 has been worked at speed and is breathing rapidly is liable to have 

 pneumonia if suddenly chilled, while an animal which has just been 

 fed is more liable to have a congestive colic if exposed to the same 

 influence, the blood in this case being driven from the exterior to the 

 intestines, while in the former it was driven to the lungs. 



Symptoms. — The symptoms of inflammation are, as in congestion, 

 • change of color, due to an increased supply of blood ; swelling, from 

 the same cause, with the addition of an effusion into the surrounding 

 tissues; heat, owing to the increased combustion in the part; pain, 

 due to pressure on the nerves, and altered function. This latter tc\?ly 

 be augmented or diminished, or first one and then the other. In 

 addition to the local symptoms, inflammation always produces more 

 or less constitutional disturbance or fever. A splint or small spavin 

 will cause so little fever that it is not appreciable, while a severe 

 spavin, an inflamed joint, or a pneumonia may give rise to a marked 

 fever. 



36444°— 16 3 



