DISEASES OF HORSES 85 



other mechanical obstructions, by pressing on the veins, retard the 

 flow of blood and cause it to back up in distal parts of the body, 

 causing passive congestion. 



The alterations of passive congestion, as in active congestion, 

 consists of an increased quantity of blood in the vessels and an ex- 

 udation of its fluid into the tissues surrounding them, but in passive 

 congestion we have a dark thick blood which has lost its oxygen, in- 

 stead of the rich combustible blood rich in oxygen which is found 

 in active congestion. 



The termination of congestion is by resolution or inflamma- 

 tion. In the first case, the choked-up blood vessels find an outlet for 

 the excessive amount of blood and are relieved ; the transuded serum 

 or fluid of the blood is reabsorbed, and the part returns almost to 

 its normal condition, with, however, a tendency to weakness predis- 

 posing to future trouble of the same kind. In the other case further 

 alterations take place, and we have inflammation. (Spl. Rpt. Horse 

 Dept. Agr. 1911.) 



INFLAMMATION. 



Inflammation is a hypernutrition of a tissue. It is described 

 as "a double-edged sword, cutting either way for good or for evil." 

 The increased nutrition may be moderate and cause a growth of new 

 tissue, a simple increase of quantity at first; or it may produce a 

 new growth differing in quality ; or it may be so great that, like lux- 

 uriant, overgrown weeds, the elements die from their very haste of 

 growth, and we have immediate destruction of the part. According 

 to the rapidity and intensity of the process of structural changes 

 which takes place in an inflamed tissue, inflammation is described 

 as acute or chronic, with a vast number of intermediate forms. 

 When the phenomena are marked it is termed sthenic; when less 

 distinct, as the result of a broken-down and feeble constitution in 

 the animal, it is called asthenic. Certain inflammations are specific, 

 as in strangles, the horsepox, glanders, etc., where a characteristic 

 or specific cause or condition is added to the origin, character of 

 phenomena, or alterations which result from an ordinary inflamma- 

 tion. An inflammation may be circumscribed or limited, as in the 

 abscess on the neck caused by the pressure of a collar, in pneumonia, 

 in glanders, in the small tumors of a splint or a jack ; or it may be 

 diffuse, as in severe fistulas of the withers, or an extensive lung fever, 

 in the legs in a case of grease, or in the spavins which affect horses 

 with poorly nourished bones. The causes of inflammation are prac- 

 tically the same as those of congestion, which is the initial step of 

 all inflammation. 



The temperament of a horse predisposes the animal to inflam- 

 mation of certain organs. A full-blooded animal, whose veins show 

 on the surface of the body, and which has a strong, bounding'heart 

 pumping large quantities of blood into the vascular organs like the 

 lungs, intestines, and the laminae of the feet, is more apt to have 

 pneumonia, congestive colics, and founder, than lymphatic, cold- 

 blooded animals which have pleurisies, inflammation of the bones, 

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



