APPENDIX

APPENDIXThe Making of the Shetland PonybyJ. COSSAR EWART, M.D., F.R.S.PROFESSOR OF NATURAL HISTORY IN THE UNIVERSITY OF EDINBURGH

J. COSSAR EWART, M.D., F.R.S.

PROFESSOR OF NATURAL HISTORY IN THE UNIVERSITY OF EDINBURGH

The Making of the Shetland Pony.

“The horses that are ancient we honour because we know not whence they came, but the new ones we slight because we know their beginning.”

TheShetland pony belongs to an ancient breed famed for its intelligence and docility, strength and hardiness, but especially remarkable because of its small size.

In a recent article on the Shetland pony it is said that “the highest authorities rather incline to the view that he is an instance of arrested development, and that all the equine race originally sprang from ancestors far more diminutive than the smallest Shetland.”

It is doubtless true that the remote ancestors of the Equidæ were small, but it does not necessarily follow that Shetland, Java, andother pigmy breeds owe their diminutive size to arrested development. A human pigmy of West Africa is as well developed as a Hottentot of South Africa, and a toy terrier is as well developed as a mastiff. There is hence noà priorireason for assuming that Shetland ponies are not as well developed—mentally and physically as perfect—as Clydesdales or Arabs. Moreover, all animals during their development repeat, more or less, their ancestral history, climb their own ancestral tree, hence if there is arrested development we should find evidence of reversion to more or less ancient types. Is there any evidence that in mind or body the Shetland is an instance of arrested development, or that he owes his diminutive size to reversion towards remote small ancestors?

It will be well at the outset to ascertain whether the small size is due to reversion or to dwarfing, induced, partly by unfavourable surroundings, partly by inbreeding and artificial selection.

The Size of the Shetland Pony.—Nature unaided has made a pigmy hippopotamus, pigmy elephants, and pigmy races of man, but there is no evidence that nature unaided in Europe or Asia in pre-glacial or post-glacial times produced a wild pigmy race of true horses—i.e., of horses with only one complete toe for each foot.

The smallest wild horses in Britain at the end of the Palæolithic period (i.e., according to a recent estimate some six thousand years ago) were apparently never under 12 hands at the withers. During the Bronze age, alike in wild and tame varieties, a size of at least 48 inches seems to have been maintained all over Europe. Further, remains from Roman military stations indicate that the smallest horses in Britain during the first century were probably never under 46 inches at the withers. It may hence be assumed that Shetland and other small breeds are not directly descended from pigmy wild races, but are the dwarfed descendants of one or more small varieties orbreeds which had long lived under domestication.

A consideration of pigmy races makes it evident that dwarfing may be either equal or unequal, that it may result in the formation of a miniature having all the leading traits of the large race to which it belongs, or give rise to a pigmy variety in which certain parts are more dwarfed than others. In some small strains of dogs the relative proportion of all the parts are practically the same as in large strains, but sometimes in a small strain not only are the limbs more dwarfed than the trunk but certain parts of the limbs are more reduced than others. An example of unequal or disproportional dwarfing we have in the dachshund. In this breed the dwarfing has been carried further in the legs than in the body, and in the forearm than in the foot. In a normally constructed small hound in which the length of the body is 390 mm., the length from the elbow to the ground is 215 mm., from the elbow to the wrist 145 mm.,and from the wrist to the end of the longest toe 95 mm. But in a typical dachshund with a body of approximately the same size (390 mm.) the length from the elbow to the ground is only 137 mm., the distance from the elbow to the wrist being 95 mm. and from the wrist to the end of the longest toe 90 mm.—i.e., in a dachshund, while the foot may only be reduced 5 mm., the reduction in the forearm may amount to 50 mm. (2 inches).

In the case of pigmy horses are the proportions of their normal ancestors invariably retained, or are the legs in some cases more dwarfed than the trunk, and as in the dachshund is the dwarfing greater in one part of the limb than in another? In Java ponies I have had under observation for some years the head and limbs bear practically the same relation to the body as in well-proportioned Arabs.

For example, in a 41-inch Java mare (fig. 1) the height at the withers, as in typical desert Arabs, is 2·7 times the length of the head,and the neck and limbs are relatively as long as in Arabs and other slender-limbed breeds.

But while in tropical islands the relative proportion of the various parts of pigmy horses may be maintained, in islands near the Arctic Circle dwarfing may imply undue shortening of the limbs, and that certain parts of the limb are more reduced than others.

A striking instance of unequal reduction we have in the Udganger or Nordlands ponies, once common in Bodo, a small island within the Arctic Circle off the coast of Norway. Fig. 2 shows that the limbs of the Bodo ponies were relatively nearly as much dwarfed as in a dachshund, while fig. 3 shows that Iceland ponies of the Nordlands type may closely agree in conformation with Exmoor and other well-built ponies of the Celtic race.

Very little is known about the make and size of the horses which first reached Shetland. The evidence as far as it goes indicates that they belonged to small varieties measuringfrom 11 to 12 hands at the withers. If horses were introduced from Norway during the Norse occupation, the majority of them would in all probability belong to the Nordlands race—i.e., the race from which the modern fjordhest is believed to have mainly sprung. Probably unequal dwarfing more or less pronounced took place at a comparatively early period in some of the smaller islands, while in the more fertile parts of the main island, and in the rich island of Fetlar, the reduction in size (as in Java ponies) would be nearly uniform. It is conceivable that some of the unimproved ponies now living in Shetland, and also some of the improved ponies bred and reared far from their ancestral island home, are as well proportioned as members of the Exmoor or Welsh breeds. One must, however, be prepared to find that not a few of the inbred pedigree ponies have undergone unequal dwarfing, one part of the limbs, as in the dachshund, having undergone more reduction than the adjacent parts.

Dwarfing in Shetland Ponies of the Celtic or Riding Type.—That well-proportioned Shetland ponies of the riding or Celtic type still exist is suggested by the measurements of Pamela and certain other fine-limbed pedigree ponies. Pamela (40 inches at the withers, 25 inches from elbow to ground, and 5·25 inches below the knee), in the form and length of the head, length of the limbs and their relation to the height at the withers, very closely agrees with the 41-inch Java pony.

The skeletons of Shetland ponies of the riding type available for study (viz., of Highland Chieftain, Egil, and Eric) also indicate that in a considerable number of cases the dwarfing is uniform. Though in many Shetland ponies the distance between the knees and the fetlocks looks very short, the front cannon-bones may be relatively as long as in thoroughbred race-horses. In Highland Chieftain[F1](fig. 4) the front cannon-bones (metacarpals) are 136 mm. long and 20 mm. wide at the middle of the shaft; in Persimmon,[F2]the famous thoroughbred 16·2 race-horse (fig. 5), the metacarpals measure 276 mm. by 38 mm. As Highland Chieftain measured 33 inches, and has cannon-bones measuring 136 mm., he was half the height of Persimmon, and has cannon-bones practically half the length. In Highland Chieftain the cannon-bones (fig. 4) are not only relatively as long as in Persimmon (fig. 5), they bear almost exactly the same relation to the bones of the forearm and arm as in Persimmon—theradius(chief forearm bone) being relatively only 8 mm. shorter, thehumerus(upper arm bone) relatively only 10 mm. longer. Nevertheless the cannon-bones of Highland Chieftain are relatively shorter than in typical Celtic ponies. In a 33-inch Shetland built on Celtic lines the cannon-bones should measure 142 mm.,hence it may be assumed the cannon-bones of Highland Chieftain have been dwarfed to the extent of 6 mm. or one-quarter of an inch.

[F1]The skeleton of Highland Chieftain (a 33-inch Shetland pony bred in Scotland) is in the American Museum of Natural History, New York; Egil’s is in the University of Edinburgh.

[F2]The skeleton of Persimmon is in the British Museum.

The only striking difference between Highland Chieftain and a typical 12-hands Celtic pony is in the face. In modern horses, while the form of the cranium or brain-box is nearly constant, the face varies both in size and in its relation to the cranium. In the wild steppe horse (Equus przewalskii) of Mongolia, which during part of the year subsists on hard dry food, the jaws are so long that the length of the face (fig. 8) is twice the width across the orbits, thus giving a frontal index of 50; whereas in a broad-browed Iceland or Highland pony the face may be only 1·6 times the width, which implies a frontal index of 60. In the Celtic race (to which Highland Chieftain mainly belongs) the normal frontal index is 54—i.e., the length of the face is 1·8 times the width—but, as in Highland Chieftain, the length of the face isonly 1·5 times the width, the frontal index[F3]is as high as 65. Further, in Highland Chieftain the profile instead of being convex as in steppe horses (fig. 8), or nearly straight as in many Exmoor ponies, was decidedly concave or dished (fig. 4). The difference between the profile of a Shetland pony and that of a steppe horse is brought out by figs. 6 and 8.

[F3]The frontal index is obtained by multiplying the greatest width above the orbits by 100, and dividing the result by the length of the face, as measured from the alveolar point to a line connecting the supra-orbital foramina.

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 islandpony 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). InNeohipparion, 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 andmore slender in the extinctNeohipparionthan in modern race-horses. In Egil the front cannon-bone is 175 mm. (6·75 inches) long and 25 mm. wide; inNeohipparionthe 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, inNeohipparionthe 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 inNeohipparionand 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 belowthe 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 limbsclosely 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.”

It was at one time the ambition of some breeders to have Shetland ponies as small as their remote three-toed Miocene ancestors. As a matter of fact, ponies smaller than some of the Miocene species have long existed in Shetland. Eric, though an average-sized pony, was at least a hand smaller than the late Miocene horse,Protohippus sejunctus, in which the front cannon-bones (fig. 9b) were 177 mm. long and 21 mm. wide—i.e., 34 mm. (1·37 inches) longer but 5 mm. narrower than in Eric; while Seedpearl (31·75 inches at the withers) and other still smaller living ponies have shorter limbs than the very ancient three-toedMesohippusfrom the Badlands of South Dakota. But while some Shetland ponies are actually smaller and have relatively decidedly shorter legsthan the horses which flourished long before man appeared on the scene, they never have three toes and their teeth are always decidedly longer if not more complex than in the most advanced Miocene species. Hence, as already said, though in Shetland ponies there is evidence of arrested growth, there is no evidence of arrested development. It has been pointed out that the facial part of the skull of Eric is so short that the frontal index is extremely high—67 instead of 54. Even more remarkable than the shortening of the face is the reduction in Eric of the capacity of the nasal chambers. In new-born foals, owing to the relatively large size of the cranium, the face is always more or less dished (fig. 7). In the case of the wild horse of Mongolia, the increase in the size of the nasal chambers soon gets rid of the dishing, and in course of time the nasal bones are bulged outwards, so as to give rise to a more or less marked “Roman-nose” (fig. 8). But in Eric andmany other Shelties of the riding or Celtic type, owing to the expansion of the nasal chambers being prematurely arrested, the profile in the adult (fig. 6) differs but little from that of the new-born foal (fig. 7).

Shetland Ponies of the Cart-horse or “Forest” Type.—For want of material nothing very definite can be said about the nature of the dwarfing of ponies of the heavy or cart-horse type. In a typical 12-hands Celtic pony the metacarpals are 200 mm. long, 27·5 mm. wide, but in a typical 12-hands “forest” horse the metacarpals are, on an average, 193 mm. long and 35·1 mm. wide. An undwarfed, thick-set, 36-inch Sheltie built on the same lines as a 12-hands “forest” horse should have metacarpals about 145 mm. in length and 26·4 mm. in width, and should measure 5·5 inches below the knee.

The measurements available indicate that in a pedigree 36-inch Sheltie of the“forest” type, the front cannon-bones will probably measure 137 mm. by 26·2 mm., that the circumference below the knee will be 5·5 inches, and the distance from the elbow to the ground 21·5 inches—in Eric (36·5 inches) the length from elbow to the ground was 22·25 inches. If these figures are approximately correct, it follows that in a 36-inch Sheltie of the cart-horse type the limbs may be at least an inch shorter than in a dwarfed 36-inch pony of the riding type, and that the dwarfing may be unaccompanied by any loss of “bone.”

This conclusion is supported by the measurements of Odin, a 38-inch pony, 6 inches below the knee; of Vulcan, a 32-inch pony, 5 inches below the knee; and of other ponies of the Londonderry type belonging to the Ladies Hope, and also by those of Everlasting, Frederick, and other thick-set Auchlochan ponies. For example, in Everlasting, a 38-inch pony, the distance from the elbow to the ground is 22·75 inches,the circumference below the knee 5·5 inches, the bone being “round,” and the shank ·5 inches broader than in the flat-boned riding pony Eric.

In heavy horses, but especially in Shire colts, one (or more) of the limbs has occasionally an extra digit ending in a well-formed hoof. In a three-weeks’ horse embryo there are no rudiments of limbs; at four weeks the limbs are represented by paddle-like structures; at five weeks the paddles contain rudiments of three toes—miniatures of the three toes ofHypohippus(fig. 20).

In ordinary circumstances the development of the outer and inner toes (ii. and iv.) is soon arrested, but occasionally one of these rudiments develops into a toe as large and complete as in three-toed Miocene horses of the “forest” type. When this happens, when in addition to the third toe there is a toe corresponding to the human forefinger, we have a marvellous instance of reversion.

If in the Shetland breed there is a tendencyto reversion, one would expect to find now and then extra digits in ponies of the heavy or “forest” type. I have, however, never heard of a Shetland pony with extra digits.

Dwarfing of the face and the reduction of the nasal chambers has apparently been carried further in some of the miniature cart-horses than in Eric and other flat-boned Shelties. In Jupiter,[F5]e.g., the head, though wider across the orbits, is shorter than in Eric, and decidedly more dished. Ancient horses adapted for a forest life had face pits in front of the orbits, which probably, like the corresponding pits in deer, lodged scent glands. Further, in ancient “forest” horses the upper lip was probably decidedly longer and more prehensible than in modern breeds. In broad-browed, big-boned Shetland ponies there is no indication of a pit for a scent gland, but there is sometimes an unusually long and decidedly mobileupper lip, which may or may not be due to reversion.

[F5]Jupiter was a 37·5 inch “elk-nosed” pony, with a girth of 54·5 inches, rounded quarters, a low set-on tail, a complete set of chestnuts, wide open hoofs, and six inches of “bone.”

The Causes of the Dwarfing of Shetland Ponies.—Given sufficient food and shelter, horses up to 15 hands—the size of the tallest prehistoric Old World wild horse—can easily be bred and reared in both the Western and Northern Islands of Scotland. On the other hand, large breeds are soon dwarfed when, in addition to a limited supply of food, the conditions during a considerable part of the year are extremely unfavourable. If Shetland ponies have not sprung from a small wild pigmy race, it may be safely asserted that their small size is mainly due to isolation in small areas where they were forced to shift for themselves under, as a rule, extremely unfavourable conditions.[F6]Obviously the environment may play a double part. It may (1) arrestgrowth by failing to provide sufficient food and shelter, and (2) it may eliminate the individuals which, by growing beyond a certain size, require during times of stress more food and shelter than are available. Considerable stress has been laid by writers on the dwarfing influence of the surroundings. It is said,e.g., that “horses taken to the barren and cold islands of Shetland become gradually smaller and hardier, like ponies, and the hair becomes thicker and longer. Long-continued exposure to such conditions ultimately results in the production of an animal like the Shetland pony, small in size, extremely hardy, able to withstand the most severe winter climate, and to subsist on a minimum of food.”[F7]It might be said that this view is supported by experiments in the Western Islands. At the beginning of the eighteenth century the Captain of Clanranald (who was killed in 1715 at the battle of Sheriffmuir) brought from Spain“some Spanish horses which he settled in his principal island of South Uist. These in a considerable degree altered and improved the horses in that and the adjacent islands. Even in 1764, not only the form but the cool fearless temper of the Spanish horse could be discerned in the horses of that island.... These at that time, both in figure and disposition, were thought the best horses observed in the Highlands, and though of low stature were judged more valuable than any other horses of the same size.” The descendants of the Spanish horses introduced by Clanranald for a time increased the size of the horses in the adjacent islands. Nevertheless, in spite of the introduction of the Spanish horses at the beginning of the eighteenth century, and the introduction of many south-country horses during the second half of the eighteenth century, the Highland and Island horses at the beginning of the nineteenth century were “sometimes only 9 and seldom 12 hands high.” Moreover, though some of them were “of an excellent form,” with“great strength in proportion to their size,” agile and spirited, many were “short necked, chubby headed, and thick and flat at the withers.”[F8]

[F6]That the conditions are now and again very trying in Shetland is proved by the death-rate among native sheep being, in some districts, from 40 to 50 per cent. during the winter of 1912–13.

[F7]‘Cyclopædia of American Agriculture,’ vol. iii. p. 34.

[F8]Walker’s ‘History of the Hebrides,’ vol. ii. 1808.

Evidence in support of the view that the descendants of the Spanish and south-country horses, introduced about 1710 and after 1745, were soon either eliminated or dwarfed, we have from Dr Johnson and others. Dr Johnson tells us that the pony he rode in Coll was very low, and that a bulky man on one of the native horses made “a very disproportionate appearance,” and, after referring to the small horses of Rum, mentions that he had heard of a yet smaller race in Barra, “of which the highest is not above 36 inches.” Barra was one of the islands which benefited by the introduction of Spanish horses by Clanranald.

That dwarfing may be the direct result of an inadequate supply of nourishment during development is suggested by the condition of fœtuses I found some years ago in a wildrabbit. The right uterine horn of this rabbit contained four young, the left eight. The eight in the left horn were as well developed as the four in the right horn, but only half the size and half the weight. Evidently the amount of nourishment available in this case was limited, and as the eight in the left horn only received as much as the four in the right horn, they were only half the size.

But while dwarfing may be, or appear to be, directly caused by the environment, there are other possible causes. Sometimes the small size of one or more members of a family or litter is due to reversion to small ancestors. For example, in a litter of five puppies bred some months ago (from parents in which West Highland and Mexican (Spanish?) blood prevails) there is marked variation in size. When these pups of mixed origin were weighed three days after birth, two males weighed 7·5 oz. each, two females 5·5 oz. each, and one male 4·5 oz. When again weighed at the end of the twelfth week, thelargest male scaled 106 oz., the smallest male 44 oz., the larger female 58 oz., and the smaller female 46 oz. In this case the small male reproduced his small Mexican great-grandsire, while the large males took after their West Highland ancestors.

But dwarfs often enough turn up in old-established “pure” breeds, and now and again a dwarf is found in an otherwise normal human family. There is no reason for supposing that such dwarfs are the result of reversion. Just as one of a litter of pups may prove a dwarf, one of five or six foals, full brothers and sisters, may prove a dwarf.

It may, I think, be assumed that in the case of horses living under natural conditions, “spontaneous variation,” without the aid of reversion, will, as a rule, provide sufficient material to admit of a variety being evolved well adapted in size and other respects for the conditions which at the moment prevail.

It need hardly be pointed out that little will be gained by speculating as to whetherdwarfing is due to the direct influence of the environment, to reversion, or to spontaneous variation.

Many breeders, more especially breeders of dogs, seem to think that dwarfing is invariably the result of inbreeding. It is doubtless true that the members of many recently formed pigmy breeds are closely inbred, but it is well to bear in mind that there are closely inbred large as well as closely inbred small breeds—that size is largely a matter of selection—that in the case of natural races size depends more on the surroundings and the extent of the range than on the consanguinity.

The view that dwarfing is caused by inbreeding is insisted on by Sir Everett Millais in a book on Rational Breeding. Sir Everett states that, though in the case of the Shetland pony the “climate, bad food, &c., had been a factor in reducing the size, the primary cause was inbreeding due to isolation.”

It seems to me, however, highly probablethat until artificial selection began in earnest about thirty years ago, inbreeding had little influence in determining the size of Shetland ponies—that isolation had been a decidedly more potent factor than inbreeding. Scottish red deer are decidedly smaller now than they were in Roman times; but this is not so much due to inbreeding as to the range of most of the herds being restricted, and to the best stags being cut off before they have a chance of improving the herd. The Scottish deer in New Zealand, though all descended from a few imported individuals, instead of dwindling in size, are larger and carry finer heads than their home-bred relatives,—the wider range and better conditions have more than compensated for the inevitable in-and-in breeding. It is doubtless true that in-and-in breeding sooner or later diminishes the vigour, size, and fertility, and, in addition, restricts variation. But under natural conditions, if the range is sufficiently extensive, occasional reversion to vigorous ancestors will preventdwarfing provided there is rigid elimination of the unfit.

If Shetland ponies are the pigmy descendants of one or more ancient races at least as tall as Exmoor and Welsh ponies, one would expect them to increase in size when bred and reared under favourable conditions. It has been again and again asserted that “the climate and comparative privation of the Shetland Isles were necessary to maintain the small stature of the ponies, and that the breed would inevitably lose this and all other characteristics if bred away from Shetland and under more generous conditions.”

Some of the ponies recently brought south from Shetland have increased so much in size that, if otherwise eligible, they could not be registered in the ‘Shetland Pony Stud-Book’—i.e., they are now over 42 inches at the withers.[F9]The majority of these tall ponies, however, are piebalds or skewbalds, which inmake and other respects resemble Iceland ponies,—if their history were traced, a piebald Iceland pony would probably be found amongst their recent ancestors. It is not surprising that young cross-bred Shetland ponies increase considerably in size when grazed on rich lowland pastures, or that now and again a pure-bred pedigree pony should grow above the recognised standard; but these exceptions only serve to prove the rule, now widely recognised by breeders, that pure-bred Shetlanders remain small however favourable their surroundings. Seeing that in the majority of pedigree ponies the dwarfing has gone so far that the metacarpals are actually shorter than in the remote three-toed Miocene ancestors, what is surprising is that there is not an immediate response to the stimuli which genial surroundings and abundant food imply.

[F9]In all probability these ponies would have measured over 40 inches had they remained in Shetland.

Some 500 years ago a female rabbit and her young were turned out on the small island of Porto Santo near Madeira. In course of time this island was so overrun with rabbitsthat it was for a time abandoned as a settlement. As the rabbits increased in number they dwindled in size, became reddish above and grey beneath, and lost the black marking from the points of the ears and the tip of the tail. Some of these Porto Santo rabbits which reached the London Zoological Gardens in 1861 reacquired the colour and markings of the common wild rabbit within four years. The Porto Santo rabbits having recovered the ancestral colours soon after reaching Europe, it might have been anticipated that the Shetland pony would recover some of his lost inches when taken to the south of England—to the area containing the remains of the 12-to 13-hands wild races from which small British breeds have mainly sprung. There is, however, no longer any doubt that the small size is, as a rule, maintained however favourable the surroundings. Why the Sheltie fails to respond to the growth stimuli which favourable surroundings so abundantly provide it is extremely difficult to explain. In the language of the day, one can onlysay that the limbs have forgotten how to grow beyond a certain size, and add that this loss of “memory” may be the result of breeding from the smallest individuals regardless of their consanguinity. In 1892 Mr Christopher Wilson, in a letter to Mr Meiklejohn, then in charge of the Bressay Stud, said:“With regard to the Shetland ponies, your great object is to keep them small.... There is no class of animal to which inbreeding can be better applied, as all you will lose by inbreeding is size, which is what you want.... To inbreed them there is only one plan. Select your very best stallion and put him to a certain number of mares, and then put all the good fillies when three years old to their father; also, select your very best mare and put her to another stallion, and go on breeding from her to the same stallion until you have a colt, then put that colt to his mother, and use the produce to breed from with the produce obtained by putting the fillies above mentioned to their father.” A better plan for fixing the size could hardly be imagined. If followed for some years the size of the bones and muscles would doubtless be so effectively stereotyped that, however much their “memory” was jogged by “fresh fields and pastures new,” there would be little or no response. Although close in-and-in breeding was undoubtedly practised, the Shetland Pony Stud-Book indicates that the advice of the originator of the “Sir George” strain of hackney ponies was not literally followed.

The Ancestors of the Shetland Pony.—From pigmy horses it seems but a step to the little “fossil” horses of bygone days. It is hence not surprising that many are led to inquire to which particular branch of the equine family tree the Shetland pony belongs.

Not many years ago it was said the horse tribe was at the start represented by a primitive race about the size of a fox but with as many hoofs as a tapir—four in front and threebehind,—that in course of time a new race arose (with three hoofs in front as well as behind) which eventually gave rise to the one-toed ancestor of all the living Equidæ.

Now, however, we know that in Eocene times there were several kinds or species of four-toed “horses” from which were derived, in the Oligocene and Miocene periods, numerous three-toed species, some of them doomed to early extinction, others to bring forth one-toed races which in due time produced the ancestors of the modern horses, asses, and zebras.

Hence it is now admitted that, in the past as in the present, the horse tribe was always represented by several species, not a few of which at times occupied the same area. It is also now admitted that the modern domestic breeds include several wild prehistoric species among their ancestors.

Is it possible to say which of the wild horses of prehistoric times contributed to the making of the Shetland pony? To be in a position tohazard an answer to this question it will be necessary to refer to the more important links which are believed to connect modern breeds withHyracotherium, generally regarded as the remote polydactylous ancestor of the horse family.

Hyracotheriumlived in the south-eastern part of England—his remains occur in the London Clay near Herne Bay and in the Red Crag of Suffolk—i.e., in deposits formed two or three or it may be six million years ago. This ancient fossil horse—though not unlike a long-faced fox terrier—Owen regarded as a relation of the Hyrax or Coney of Palestine, hence the nameHyracotherium. Evolved in Western Europe—perhaps in England—this primitive small-brained terrier-on-hoofs not only wandered across Europe and Asia, but actually crossed into America—then freely connected with north-eastern Asia—and ranged at least as far south as New Mexico. So conservative was this small forerunner of the great horse family that the American representative from the Wasatch deposits only differs from the parent form in having slightly more complex teeth. The fore and hind foot of the American variety ofHyracotherium—generally known asEohippus—is represented in fig. 10, and fig. 12 gives a restoration ofEohippus.

Though at the beginning of the Eocene period the milk-givers were backward and small (Eohippuswas probably only 12 inches at the withers), the struggle for existence was probably keen enough. At any rate, the European varieties ofHyracotheriumeither died off without leaving descendants or gave rise to odd-toed ungulates which took no part in forming the modern Equidæ. But for the American branch of theHyracotheriumfamily there would have been no horses. In course of timeEohippuswas supplanted byProtorohippus(a 14-inch horse longer in the limbs and with more complex teeth), which towards the close of the Eocene period gave place to the still more specialisedOrohippus. It may be mentioned thatEpihippus, a slightly modifieddescendant ofOrohippus, may have lived side by side with the remote ancestor of the camels—a quaint even-toed ungulate about the size of a “jack-rabbit.”

The limbs ofOrohippus[F10]are represented in fig. 11, and a restoration is given in fig. 13.

[F10]In the Yale collection there are five species ofOrohippusfrom New Mexico and Wyoming.

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