CALLOSITIES AND ERGOT. 9 



occurs on the inner side of the hind-limb some distance below the 

 tarsus, or hock (%. 8). This hind-callosity is absent in certain 

 ponies from Iceland and the Hebrides as well as, it is reported, in 

 some horses from North Africa ; and is always wanting in the Ass, 

 the Zebras, and all other members of the family. The front callosity 

 is more warty in the Horse than in any other species of the family. 



These structures are evidently of the type commonly called 

 rudimentary, that is to say, they are the decadent remnants of 

 organs once functional. They have been regarded as representing 

 glands. Important evidence in favour of this view is the fact 

 that when cut the callosities yield a fluid which will attract other 

 horses, and will likewise cause dogs to keep quiet when the 

 premises of their masters are invaded ; such a fluid being almost 

 certainly derived from an ancestral scent-gland. 



Specimens of the legs of the Horse (N.H. 71, 72), Ass (N.H. 69, 

 70), and Zebra (N.H. 68) are exhibited in the large case in the 

 central archway on the north side of the hall to illustrate these 

 remarkable structures. Near by are shown in spirit portions of 

 the bind-legs of two unborn colts (N.H. 96, 96 a) in order to 

 demonstrate that the position of the calosity (flg. 9) is the same as 

 in the adult, and thus to refute the suggestion that these structures 

 represent one of the foot-pads of less specialized Mammals. 



In the same case are displayed specimens of the limbs of Deer 

 with glands situated in positions not very dissimilar to those 

 occupied by the callosities of the Horse, 



In old veterinary books the callosities, which were supposed 

 to be due to disease, are called sallenders (from the French 

 Solandre), or mallenders. They are sometimes called '^castors." 



The true representative of a foot-pad is the ''ergot," 

 I he trgoi. ^^. ^^^^n i^orny knob projecting from the hind surface of 

 the fetlock of the Horse. A specimen (N.H. 93, fig. 10) showing 

 this is displayed in the same case, where the foot of a Tapir 

 (N.H. 94, fig. 11, A) and another of a Dog (N.H. 95, fig. 11, B) 

 are also exhibited, in order to show the correspondence of the 

 central pad with the Horse's ergot. 



.In this place certain interesting abnormalities which 



occasionally make their appearance in Horses may be 



Horses. eonveniently noticed. The most remarkably of these 



are connected with the skull. The specimens exhibited include 



