EXTRA DIGITS AND DIGITAL REDUCTIONS 347 



antelope, bison and ox ; these animals roam the open plain and upland, 

 and the outer toes would be of no use except for the occasional support 

 of the foot when these animals enter the water to drink. We find, 

 therefore, that only the small hoofs of the reduced toes persist. In 

 the foot of the camel and giraffe even these vestiges have disappeared, 

 as their habitat has long been the dry, sandy plain. 



From these observations it seems plain that among ungulates the 

 functions of the digits have been affected by the habitat of the various 

 animals; and that there is a direct relation between the degree of 

 digital reduction and the character of the country traversed. The 

 use of the foot as an organ of locomotion alone, and the assumption 

 of the digitigrade posture, were the primary factors producing reduc- 

 tions of the toes; the degree of such reductions and the type of foot 

 produced have been dependent upon the habitat of the animals. The 

 artiodactyl foot was formed in adaptation to semi-aquatic habits, and 

 as the animals changed their habitat to ' terra firma ' a further reduc- 

 tion of the digits resulted. The perissodactyl, or odd-toed, type of 

 foot, began with the assumption of the digitigrade posture by animals 

 which traversed solid ground, and the digits were further reduced as 

 the digitigrade posture was developed to perfection. 



It has been assumed that those digits which were useless would dis- 

 appear. There is evidence that if they were not reduced they would 

 be not only useless, but of distinct disadvantage to the animals. The 

 writer has observed that the extra hallux rarely occurs on the pes of 

 hunting dogs; when it does occur it is frequently injured and some- 

 times completely torn away. It is also noteworthy that the extra toe 

 is most often found on the pes of the St. Bernard and Newfoundland, 

 in which breeds it may be of some use for swimming, and walking 

 through deep snows. It has been observed, too, that the small hoofs 

 of the sheep and deer grow rapidly on the second and fifth digits, but 

 are normally worn away by daily use. If these animals are kept in 

 unnatural surroundings, as when sheep are deprived of rocky pasture, 

 or deer kept in zoological gardens, the hoofs of the reduced digits will 

 grow long, curved and twisted to such an extent as seriously to impede 

 locomotion. We can readily see that should the wild deer or sheep 

 change its habitat to the smooth footing of the open plains, the same 

 abnormal growths might occur and hinder rapid locomotion. Varia- 

 tions tending toward the reduction of these digits would favor the sur- 

 vival of their possessors, and give rise to the type of foot found among 

 the antelopes, cattle and giraffes. 



In conclusion it may be of interest to speak briefly of the digital 

 reductions which have taken place in the foot of the running birds 

 (Katitse). The most primitive of the birds exhibited the digitigrade 

 posture, but walked upon the ball of the foot. This may have caused 

 the reduction of the fifth digit (which early disappeared), and cer- 



