In the case of Egil[F4] the dwarfing of the limbs seems to have been more pronounced. Egil may be regarded as an unimproved 40-inch pony; he met his death some forty years ago by falling over a cliff near Hillswick, Shetland—i.e., before the Marquis of Londonderry set about making a short-limbed strain suitable for pit work. A comparison of the skeleton of Egil with that of an Exmoor pony in the British Museum shows that in the northern island pony the limbs were relatively shorter by one inch, and the face by half an inch, than in the southern moorland pony, but, notwithstanding the shortening of the limbs, the front cannon-bones in Egil, as in fine-limbed prehistoric races, are in length seven times the width.
[F4] Egil (a four-year-old black stallion) belonged to Mr Anderson, Hillswick.
As Egil probably belonged to an unimproved stock, it may be asked, Does his skeleton lend support to the view that modern pigmy horses reproduce, apart from their size, the characteristics of their remote ancestors?
In Miocene, as in prehistoric times, there were light as well as heavy horses, but in the light as well as in the heavy each limb had three hoofs (fig. 18). In Neohipparion, a late Miocene three-toed horse, about 40 inches at the withers, the skull is longer by 12 mm., and the molar teeth are more specialised than in Egil, the 40-inch modern island pony. In the Equidæ the cannon-bones are especially interesting; strange as it may appear, the middle cannon-bones are relatively longer and more slender in the extinct Neohipparion than in modern race-horses. In Egil the front cannon-bone is 175 mm. (6·75 inches) long and 25 mm. wide; in Neohipparion the corresponding bone has a length of 210 mm. (8·25 inches)—is longer than in a 48-inch Exmoor pony,—and is so slender that the length is nearly nine times the width—i.e., relatively more slender than in desert Arabs. Further, in Neohipparion the middle metatarsal (hind cannon-bone) is as long as the femur (thigh-bone), whereas in even the 16·2 hands race-horse Persimmon (fig. 5) the middle metatarsal is only three-fourths the length of the femur. But, though in the 40-inch Shetland pony the skull and the cannon-bones are actually shorter than in the ancient 40-inch Miocene horse (Neohipparion), the second and fourth digits are as rudimentary, are as much “splint” bones, in Egil as in Arabs and thoroughbreds. There is hence no evidence of reversion in Egil, no attempt to reproduce the second and fourth toes, which, though shorter, were as complete in Neohipparion and his three-toed contemporaries (figs. 19 and 20) as the large functional middle toe,—in other words, in pigmy horses there is evidence of arrested growth but not of arrested development. In Egil, as in Highland Chieftain, there is also evidence of arrested growth in the facial part of the skull; the profile is concave and the frontal index high (65) as in Highland Chieftain.
Having seen that, apart from the face, the only essential difference between the skeleton of an unimproved Shetland and the skeleton of an Exmoor pony is a difference in size, let us next direct attention to the skeleton of Eric, a 36·5-inch improved pedigree pony of the riding type, for some time in the possession of Mr Charles M. Douglas of Auchlochan. In Eric, who died when six years old, the fore limb from the elbow to the ground was 22 inches, the length from the point of the hock to the ground 15·4 inches, the circumference below the knee 5·25 inches, and the width of the fore-shank 1·2 inches. All four ergots were present, but the hind chestnuts were absent. Though the setting-on of the tail, the somewhat rounded hindquarters and the presence of ergots, indicated that Eric, like practically all modern Shelties, included horses of the “forest” type amongst his ancestors, his skull, teeth, and limbs made it evident that he mainly belonged to the Celtic or riding type.
In Eric the face (fig. 6) is so short that the frontal index is 67, the length being only 1·4 times the width instead of 1·8 as in 12-hands ponies of the riding type. The length of Eric’s head when alive was 410 mm. (16¼ inches). A typical Celtic pony with a 410 mm. head measures 40 inches at the withers. Eric, though having the head of at least a 40-inch pony, only measured 36·5 inches. It may hence be assumed that, through dwarfing, his total height was reduced by 3·5 inches.
Further, as Eric’s metacarpal (fig. 9a), instead of measuring 166 mm. (the normal length in a 40-inch pony), had only a length of 143 mm., it follows that practically one inch of the dwarfing was due to a reduction in the length of the cannon-bones. Moreover, as Eric actually measured 36·5 inches, his metacarpals should have measured 152 mm. instead of 143 mm.—143 mm. being the length in a normal pony measuring 34 inches at the withers.
Though Eric had the head and trunk of a 40-inch pony and the metacarpals of a 34-inch pony, the metacarpals bear the same relation to the radius and the humerus as in Persimmon—i.e., in Eric the relative lengths of the different parts of the limb were maintained (not lost, as in the dachshund) during the dwarfing process.
Although the cannon-bones in Eric had been considerably reduced in length, they had not been reduced in width—i.e., they are as wide as the metacarpals of the 40-inch Shetland pony Egil, in which the limbs closely conform to the Celtic type. It thus appears that, in the case of ponies, reduction in height at the withers, and especially in the length below the knee, is not necessarily accompanied by loss of “bone.”