50 MATERIALS FOR A MEMOIR ON 



Proposition that the Foot strikes the Ground by the Outer Border. 



This movement most probably takes place in a constant manner 

 in all quadrupeds. Huxley* describes the act in the chimpanzee 

 as though it were peculiar to that animal. In the horse the 

 movement is well seen in series 601, Figs. 3 and 4, left hind foot. 

 It is also seen in Fig. 4 of the right foot of the same series. The 

 action is well seen in series 581, Figs. 10 and 11. (See pp. 42, 84, 88.) 



The foot in all animals excejjting the horse (and even in this 

 single-toed form the movement of the foot is in nearly all essen- 

 tials the same) is carried forward in semipronation. After the 

 foot strikes the ground on the outer l)order pronation begins, and 

 is completed by the time the perpendicular line is reached. The 

 foot leaves the ground by the inner border (the toes being succes- 

 sively abducted), so that the pressure of the body is borne from 

 without inward across the foot. (See Fig. 4, p. 73.) The foot 

 is always everted as it leaves the ground. In a plantigrade animal, 

 as the raccoon, the foot is carried during the last part of recover 

 nearly parallel to the plane of support. In the rapid motion of 

 ungulates and of the horse the foot may actually touch the ground 

 nearly to the hock. (See p. 43.) In backward strain the hock or 

 heel is gradually raised, and at the end of strain the animal is 

 seen touching the ground by the tip of the inner functionally active 

 toe. In the horse the foot leaves by the tip of the hoof. It is 

 likely that the degree of impact of the outer border of the foot 

 will be found to correlate with the degree of development of the 

 calcaneo-sural joint,t since the weight must be carried along the 

 outer border to the rest of the limb. At the end of backward 

 strain the limb from the knee distally is in the same line. 



The entire series of changes from semipronation to pronation, 

 as studied in connection with the transfer of weight across the 

 foot, is well seen in the tiger (series 729 and 730; see also p. 85). 



The Eve>'sion of the Foot. 

 The moment flexion begins eversion is established, and the limb 

 becomes angulated outward at the ankle. The main axis of the 

 proximal facet of the astragalus is correlative with the degree of 



* Medical Times and Gazette, April, 18G4, 398. 



f A name proposed for the joint existing between the fibular process of the . 

 calcaneura and the fibula, or the tibia. 



