286 BEEEDING 



THE RATE OF GROWTH IN THE HORSE ^ 



Some years ago certain naturalists were wont to maintain that jilants 

 and animals had reached their present stage of development through the 

 operation of internal (innate) forces. Now, however, the belief is all but 

 universal that organisms are what they are to-day because of the operation 

 of external forces — that they have reached their present stage through the 

 ever-present influence from generation to generation of the external sur- 

 roundings or environment. If, during the past, the environment (which 

 includes not only the food, temperature, and other like influences, but also 

 the influence living things have on each other) has been the means of 

 producing so marvellous results — of not only causing variation but also of 

 playing the part of the selector, — it may be safely assumed that changes 

 in the external conditions may even in a single lifetime lead to very 

 decided modifications — not necessarily of a permanent (hereditary) kind — 

 in, say, the size and fitness, the time at which maturity is reached, and 

 more especially in the germ-cells from which the next generation springs. 



That in the case of the horse the external conditions or environment 

 count for something, a glance at the history of the Equklce aftbrds sufticient 

 evidence. In early Eocene times the rejDresentatives of recent horses were 

 small-brained, primitive, five-hoofed creatures, about the size of a wolf, but 

 at the most semi-plantigrade. As age succeeded age the outer digits (1 and 

 5) gradually dwindled, and at length Hi^jparion ajjpeared on the scene, 

 a creature decidedly equine in form, and only essentially differing from the 

 horse of to-day in its teeth and in its limbs, each limb bearing three 

 complete hoofs, as in the rhinoceros. 



At a still later period the evolution of the horse was carried a stage 

 further by the shrinking within the skin of the second and fourth digits, 

 already quite useless in Hipparion and in the three-toed horse (Proto- 

 hippus) of the New World. 



Like Hipparion (many fossils of which have been unearthed near 

 Athens), the true horse, during at least the Reindeer period in Europe, 

 was of a considerable size. This conclusion is supported by the size of the 

 petrified remains in the Ehone valley, where for a time the horse afforded 

 abundant sport for Palaeolithic man. Just as in olden times the elephant 

 in cei'tain areas dwindled in size to form pigmies measuring sometimes only 

 36 inches, so the horse gradually dwindled to form certain pigmy breeds 

 which (as in the Shetland Islands) were often as small as the little ele- 

 phants that in olden times flourished in what is now the Island of Malta. 



^ By Professor Cossar Ewart in the Live Stock Journal Almanac. 



