480 



Tumors or other mechanical obstruction, 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, consist 

 of an increased quantity of blood in the vessels and an exudation of 

 its fluid into the tissues surrounding them, but in passive congestion 

 we have a dark thick blood which has lost it oxygen, instead of the 

 rich combustible blood rich in oxygen which is found in active con- 

 gestion. 



The termination of congestion is by resolution or inflammation. In 

 the first case, the choked-up blood vessels find an outlet for the exces- 

 sive 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 predisposing to 

 future trouble of the same kind. In the other case further alterations 

 take place, and we have inflammation. 



INFLAMMATION. 



Inflmnniatimi is a hypernutrition of a tissue. It is described by 

 Dr. Agnew, the surgeon, 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, as a cancer; 

 or it may be so great that, like luxuriant, overgrown weeds, the ele- 

 ments 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 take place in an inflamed tis- 

 sue, 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 inflamma- 

 tions are specific, as in strangles, the horsepox, glanders, etc., where a 

 characteristic or specific cause or condition is added to the origin, char- 

 acter of phenomena, or alterations which result from an ordinary 

 inflammation. An inflammation may be circumscribed or limited, as 

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

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

 may be diffuse, as in severe fistulas of the withers, in 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 inflamma- 

 tion are practically the same as those of congestion, which is the initial 

 step of all inflammation. 



Tlie temperament of a horse predisposes the animal to inflammation 

 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, the 



