22 DADD’S VETERINARY MEDICINE AND SURGERY. 
F. Dun, a lecturer in the Edinburgh Veterinary College, tells us 
that diarrhea 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 animala 
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 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 ap 
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 bi 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 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 con- 
tact with them, permits the passage of the fluid parts of the blood, 
giving rise tc 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- 
