THE POSITIONS OF THE ARTHRA. 93 



The individual carpalia are not easily distinguished, but the 0. 

 pistforme is seen on the right side ; see Fig. 47. 



221. At the proximal end of the femur is a marked process, 

 the trochanter, which is naturally visible in the lateral view of the 

 bone, but normally has a caudal position. At the distal end of the 

 same bone are the cephalic and caudal ("inner and outer") con- 

 dyles. 



At the convexity of the knee, and thus normally dorsad of the 

 joint, is the patella, which answers in some respects to the olecranon, 

 but is really only a very large 0. sesamoideum. 



The tibia is seen to be both larger and longer than the fibula, 

 which indeed does not enter into the composition of the knee. The 

 malleoli, cephalic and caudal (internal and external), are slight 

 elevations of the distal ends of the tibia and fibula respectively. Of 

 the tarsalia, the prominent calcaneum is easily recognized. 



222. In ordinary locomotion neither the palm nor the sole are 

 in contact with the ground excepting at the junction of the metacar- 

 pal and metatarsal regions with the digits and dactyls ; the body is 

 supported upon the ball of the foot and the dactyls and upon the 

 corresponding parts of the manus, and the cat is thus a typical 

 digitigrade. We can imitate its condition so far as concerns the 

 elevation of the heel and the support of the body mainly upon 

 the ball of the foot ; but the human digits and dactyls can- 

 not be brought into the state of the cat's, where the proximal 

 phalanges are flexed dorsad, the intermediate ventrad, and the 

 distal ones again dorsad so as to keep the sharp claw points off 

 the ground. 



223. The Positions of the Arthra. It will be noted that the 

 arthra of the arm are ventrad of the corresponding arthra of 

 the leg, although the manus and pes are upon the same plane, 

 and the vertebral ends of the scapula and ilium are at nearly the 

 same level. 



Since there is little difference in either length or inclination 

 between the humerus and femur, and the radius and tibia, this 

 difference in the levels of the arthra must be associated with the 

 greater length of the pes as compared with the manus, and with both 

 the length and more nearly vertical direction of the scapula as com- 

 pared with the ilium. 



Notwithstanding the popular designation of the wrist of a horse as its " knee," it 

 should be kept in mind that the true knee of the mammalian quadruped is a joint 



