20 DADD'S VETERINARY MEDICINE AND SURGERY. 



eased, external or iutemal — are transmitted to the offspring; oi, 

 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 (t j 

 ill-formed head; for high and well-developed or for low and weak 

 withers; for fine, strong, and well-turned, or for coarse, weal\, 

 and ill-formed limbs. Peculiarities of color often extend through 

 many generations, and are so constant in their transmission i\i 

 sometimes to form one of the distinctive characteristics of a raw. 

 Indeed, most breeds of horses have a prevailing color, to whic'-i 

 there are few exceptions. The heavy horses of Lincolnshire, for 

 example, are generally of black; the Cleveland, bay; and the 

 wild horses of the plains of Eastern Siberia, dun. Particuhif 

 markings, also — as white spots on various parts of the body, staifl 

 and blazes on the face, one or more white feet or legs — often con- 

 tinue for many generations, a-nd 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 j 

 curbs, where the os calcis is small 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 

 qpon the altered conformation or texture of the parts specially 



