22 DADD'S VETERINARY MEDICINE AND SURGERF. 



F. Dun, a lecturer in the Edinburgh Veterinary College, tolls ua 

 that diarrhea and colic are, to a certain extent, hereditary, •'* inas- 

 much as th(;y 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 bo 

 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 among the different functions of diges- 

 tion, 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 no- 

 toriously 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 b( st management and 

 most efficient systems of breeding. Such characters indicate pro- 

 clivity 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 contraction of the mus- 

 cles which materially aid circulation are wantmg, 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 coq- 

 tact 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 sim- 

 ple swelled legs also give rise to the more serious affection known 

 as weed, 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 waste. Food is as- 

 similated 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 situated in the hinder extremi- 



