Hereditary Diseases of Horses. 



109 



much below average as themselves. In similarly unfavourable 

 circumstances, these again do not reach the size even of their 

 own immediate parents, and procreate a still smaller progeny. 

 Conditions favourable to growth and improvement operate in a 

 similar manner. They improve each individual, and the descend- 

 ants of each inherit to a greater or less degree the improvements 

 on the parent stock. Animals, then, are altered by circum- 

 stances, and transmit to their progeny their altered forms. Thus, 

 after a few generations, the external characters of a breed are 

 often greatly modified, and hence have arisen the permanent 

 varieties of horses and cattle met with in different parts of the 

 kingdom — the tall heavy horse of the Lincolnshire fens, the 

 light, active, but powerful thorough-bred, the small pony of 

 Shetland — and amongst cattle, the short-horned, the Ayrshire, 

 and West Highland breeds, and many others — varieties which 

 have a common origin, but which are now so distinct and per- 

 manent that each produces a progeny with its own distinctive 

 characteristics. Thus, even acquired and artificial habits may 

 become hereditary. Certain districts are famous for their trot- 

 ting horses, and many Irish hunters are remarkable for their pe- 

 culiar style of leaping. Some years ago the Earls of Morton and 

 Zetland imported from Dongolia, in Upper Egypt, several entire 

 horses, which were remarkable for their high and prancing action. 

 Their progeny, both out of thorough-bred mares and those of the 

 heavier breeds, inherited the action of the sires to such a de- 

 gree that they had all to be sold as carriage-horses, being unfit 

 for racing, hunting, or almost any other kind of work. Prichard 

 states, in his ' Natural History of Man,'* that the horses bred on 

 the table-lands of the Cordilleras " are carefully taught a peculiar 

 pace, which is a sort of running amble ;" after a few generations 

 this pace becomes a natural one, young untrained horses adopting 

 it without compulsion. But what is still more curious is the fact, 

 that, if these domesticated stallions breed with mares of the wild 

 herds which abound in the surrounding plains, they " become the 

 sires of a race to which the ambling pace is natural and requires 

 no teaching." " The hereditary propensities of the offspring of 

 Norwegian ponies," says Mr. T. A. Knight, in a paper read be- 

 fore the Royal Society in 1837, " whether full or half bred, are 

 very singular. Their ancestors have been in the habit of obeying 

 the voice of their riders, and not the bridle, and the horsebreakers 

 complain that it is impossible to produce this last habit in the 

 young colts ; they are notwithstanding exceedingly docile and 

 obedient when they understand the commands of their master. 

 It is equally difficult to keep them within hedges, owing, per- 



* Second Edition, p. 35. 



