26 DADD’S VETERINARY MEDICINE AND SURGERY. 
eased, external or internal—are transmitted to the offspring; or 
in common phraseology, are predisposing and hereditary. 
“ Among horses and cattle, we find, as in the human subject, 
ample illustration of the hereditary tendency of external form, 
disposition, habit, and disease. The parent transfers to its off- 
spring size, shape, and general conformation similar to its own; 
and the aphorism, ‘like produces like,’ is as applicable to faulty 
and disproportioned as to beautiful and symmetrical form, to dis- 
eased and debilitated as to healthy and vigorous constitution, to 
gentle and tractable as to fiery and indomitable disposition. The 
size, weight, general appearance, expression of countenance, fleet- 
ness, and temper of the horse are all hereditary. Many illustra- 
tions might be given of particular families being remarkable, 
during several generations, for good or bad points, as for well a) 
ill-formed head ; for high and well-developed or for low and weak 
withers; for fine, strong, and well-turned, or for coarse, weah, 
and ill-formed limbs. Peculiarities of color often extend through 
many generations, and are so constant in their transmission aa 
sometimes to form one of the distinctive characteristics of a racv, 
Indeed, most breeds of horses have a prevailing color, to which 
there are few exceptions. The heavy horses of Lincolnshire, foe 
example, are generally of black; the Cleveland, bay; and the 
wild horses of the plains of Eastern Siberia, dun. Particulae 
markings, also—as white spots on various parts of the body, stata 
and blazes on the face, one or more white feet or legs—often con- 
tinue for many generations, and are peculiar to certain families, 
“There are some maladies in which it is comparatively easy to 
trace the connection between conformation and disease. In the 
horse, certain sorts of limbs notoriously predispose to certain dis- 
eases. Thus, bone spavins are most usually seen where there is 
a disproportion in the size of the limb above and below the hock; 
curbs, where tlie os calcis is sma]] and the hock straight; strains 
of the tendons of the fore-leg, where the limb is round and the 
tendons and ligaments confined at the knee; and navicular dis- 
ease, where the chest is narrow and the toes turned out. Among 
horses so formed, these diseases are unusually common, and are 
developed by causes which would be quite inadequate to produce 
them in animals of more perfect conformation. But it appears to 
us that internal and constitutional hereditary diseases also depend 
upon the altered conformation or texture of the parts specially 
’ 
