Hereditary Diseases of Horses, 



121 



rejected, as likely to produce stock with weak eyes, and sus- 

 ceptible of that very serious disease, periodic ophthalmia. 



Diarrhoea and Colic are to a certain extent hereditary, inas- 

 much as they are very prone to attack horses of particular form 

 and constitution, as those with narrow loins, large flat sides, and 

 of what is generally termed a washy appearance. If such animals 

 be overworked, especially soon after being fed, if their food be 

 suddenly changed, or if they be allowed an unusual quantity of 

 fluid, they are almost certain to be attacked either by purging or 

 colic. The tendency to these diseases appears in such cases to 

 depend on a want of adjustment among the different organs of 

 the body ; a want of balance amongst the different functions of 

 digestion, circulation, and respiration. 



Many farm-horses, as well as others without much breeding, 

 are remarkable for consuming large quantities of food, for soft 

 and flabby muscular systems, and for round limbs containing 

 an unusual proportion of cellular tissue. These characters are 

 notoriously hereditary, of which indubitable evidence is afforded 

 by their existence in many different individuals of the same stock, 

 and their long continuance, even under the best management and 

 most efficient systems of breeding. Such characters indicate 

 proclivity to certain diseases, as swelled legs, weed, and grease. 

 If horses of this description stand long, the circulation of the blood 

 through the limbs is retarded ; for, as the contractions of the 

 muscles which materially aid circulation are wanting, the blood 

 in the veins rises with difficulty against its own gravity, while the 

 soft and lax condition of the venous coats, and of the muscles 

 in contact with them, permits the passage of the fluid parts of the 

 blood, giving rise to a serous effusion which is soft and pits on 

 pressure. This anasarcous condition, although troublesome and 

 frequently recurring, is easily removed by friction, exercise, or a 

 little physic, and does not unfit the animal for ordinary work. 



But the same conformation and constitution which induce 

 simple swelled legs, also give rise to the more serious affection 

 known as iceed, or a shot of grease. This consists in a disturbance 

 of the balance which naturally subsists between the waste of the 

 system and the supply of new material to repair that w aste. Food 

 is assimilated in larger quantity than the wants of the system 

 require, the chyle so formed accumulates in the absorbent vessels 

 and glands, which become in consequence irritated and inflamed. 

 That part of the absorbent system situate in the hinder extremities 

 is usually the principal seat of the disease. The animal suddenly 

 becomes lame, the inguinal and other glands in the groin 

 become enlarged and very painful, and the swelling and pain 

 gradually extend downwards along the course of the absorbents, 

 whilst the limb becomes a great deal larger than its natural size. 



