DEVELOPMENT OF GREAT SIZE IN THE DRAFT HORSE 



TH !•] skeleton of a \('r\- lar^c (liat'( lioisc is cxliihit cd to show the 

 cxtrcMiu" (l(*V(>l()i)m('nt of size in (liis l)i('(>(l. It has hccn pholo- 

 ^lapluMl witli th(* skeleton of a Shetland pony to show two ex- 

 tremes in domestic hoi'ses (Fig. 2;')). The following is a table of measure- 

 ments of th(> two specimens. 



(JiANT Draft IIousk Shetland Pony 



llright at shoulders (i ft. 1 in. (18)4 hands) 2 ft. {)% in. (H^-^ hands) 



Weight in life 2370 Ihs. 170 Ihs. 



Bulk of humerus 118/4('U. in. 9)2 cu. in. 



Bulk of femur 188 eu. in. 13/2 <'U. in. 



The pose chosen for the mounting of this specimen is one of inaction, 

 designed to express quiet restfulness, in contrast to the running action of 

 the race horse, to be mentioned later. It shows also a habit peculiar to 

 horses, that of alternately resting the hind legs. Almost the entire weight 

 of the hind quarters is supported on the extended left leg, while the right 

 hind leg rests in a more flexed position and hangs perfectly lax. The 

 pelvis also seems to hang, as it were, from the left hip joint, tilting ver\^ 

 much to the right and slightly twisting the vertebral column. 



A peculiar function of the patella (kneecap) in the horse is shown in 

 the left knee joint or stifle. While the Umb is extended and supports the 

 animal's w^eight, the patella rests on a projecting articulation of the 

 femur, so that the knee is locked in an extended position b}- a very strong 

 Ugament w^hich holds the patella at a fixed distance from the tibia below, 

 thus sustaining the weight required of it with comparatively little mus- 

 cular exertion. 



An abnoimal peculiarity of this specimen is a. pair of supernumerary 

 molar teeth, which appear at the posterior end of the upper set. Having 

 no opposing teeth in the lower jaw upon which to w^ear, they have pro- 

 truded down into the gum and must have caused the animal consider- 

 al^le discomfoi-t. 



THE SHETLAND PONY 



ITife highly probable that the Shetland pony is derived from practically 

 the same wild stock as the very much larger draft horse, but has been 

 reduced in size by adverse conditions to which it was subjected in the 

 cold and barren Shetland Islands with their limited area, and also b}' 

 having been systematically bred for the smallest possible size. 



Figure 25 shows the skeleton of an exceptionally small pony which 

 was secured through the Whitney fund. This pony was bred in Scotland 

 and obtained through the kindness of Professor J. C. Ewart of the Uni- 

 versity of Edinburgh. The skeleton represents the grazing action. It 



43 



