DISEASES OF HORSES 83 



recommended, but is of very slight value except to prolong the life 

 of the patient. Among such drugs may be mentioned strychnin (1 

 grain three times daily) or potassium iodid (2 to 5 drams daily) for 

 their alterative action. 



During the course of treatment care should be taken not to ex- 

 cite the sexual ardor of the patient, as this under all circumstances 

 augments the symptoms, and indeed the act of copulation, in the 

 mare especially, may revive the symptoms of the disease in the acute 

 stage when to all external appearances the animal had recovered 

 from a previous infection. 



Method of Eradication. Sanitary measures looking to the 

 eradication of dourine must depend on the principle that horses in- 

 fected with dourine should be excluded from breeding. This action 

 is well founded, for, in spite of the possibility of cure, there are as a 

 matter of fact frequent relapses, and further, trypanosomes may 

 exist for months in the sexual organs of the apparently cured ani- 

 mal. Therefore, it is very essential to destroy the diseased mares 

 and to castrate the affected stallions. The objection to spaying 

 mares is that if they should be sold and attempt to breed, the disease 

 may be contracted by the serving stallion and thus spread. On the 

 other hand, stallions which are castrated before the appearance of 

 paralytic symptoms become sound and well, but the stallions even 

 after castration will frequently serve mares. They should therefore 

 be prevented from mingling with mares for a month after the ulcers 

 are healed. (B. A. I. Bui. 142; Spl. Rpt. Horse, Dept. Agr. 1911.) 



CONGESTION. 



Congestion is an unnatural accumulation of blood in a part. 

 Excessive accumulation of blood may be normal, as in blushing or 

 in the red face which temporarily follows a violent muscular effort, 

 or, as in the stomach or liver during digestion, or in the lungs after 

 severe work, from which, in the latter case, it is shortly relieved by 

 a little rapid breathing. The term congestion, however, usually in- 

 dicates a morbid condition, with more or less lasting effects. Con- 

 gestion is active or passive. The former is produced by an increased 

 supply of blood to the part, the latter by an obstacle preventing the 

 escape of blood from the tissue. In either case there is an increased 

 supply of blood, and as a result increased combustion and augmented 

 nutrition. 



Active Congestion. This is caused by (1) Functional activity. 

 Any organ which is constantly or excessively used is habituated to 

 hold an unusual quantity of blood ; the vessels become dilated ; aii<i 

 if overstrained the walls become weakened, lose their elasticity, and 

 any sudden additional amount of blood engorges the tissues so that 

 they can not contract, and congestion results. Examples: The 

 lungs of a race horse, after an unusual burst of speed or severe 

 work, in damp weather. (2) Irritants. Heat and cold, chemical 

 or mechanical. Any of these, by threatening the vitality of a tissue, 

 induce immediately an augmented flow of blood to the part to fur- 

 nish the means of repair a hot iron, frostbites, acids, or a blow. 

 (3) Nerve influence. This may produce congestion either by act- 



