40 INTR OD UCTION. 



is not easy, with most Mammals, to replace them in the normal position. 

 It may, however, be readily accomplished with ail orang, and without much 

 difficulty with the arms of a cat or a child. 



The student may exemplify the normal position of the arms approxi- 

 mately by getting upon all-fours, placing the palms upon the floor at either 

 side, with the fingers pointed laterad ; the convexities of the elbows should 

 then be made to look dorsad and laterad, upward and outward. If now the 

 arms be extended laterad to their utmost length, still keeping the palms 

 against the floor, and the elbows away from it, the limbs will have nearly 

 the position shown in figures 6 and 7. 



81. Limb Segments. With the cat, as with most air-breathing 

 Vertebrates, each limb presents at least three divisions or seymenta, con- 

 nected with each other and with the soma by three arthra (joints or 

 articulations). 



These segments and arthra are thus proximal, intermediate, and distal. 

 As shown upon the right of the diagram, the proximal segments are 

 bracliium (upper arm) and meros (thigh). The intermediate segments are 

 antebrachium (forearm) and cms (leg proper). The distal segments are the 

 manus (hand) and. pes (foot). 



The entire limbs are joined with the trunk by the shoulder and hip 

 joints, while the elbow and knee intervene between the brachium and ante- 

 brachium, the meros and eras, and the wrist and ankle between the ante- 

 brachium and manus, the crus and pes respectively. 



The technical names for the arthra placed in parenthesis are those which were pro- 

 posed in 1873 by the senior author (10, 18) ; but as they have not been generally adopted 

 they are not insisted upon here. 



Each manus and pes also presents a threefold division, carpus, metacarpus, 

 and digits (thumb and fingers) ; tarsus, metatarsus, and dactyls (toes). 



The distinctive names for the digits and dactyls are placed under them. 

 The primus (great toe) is represented by a dotted line, in consideration of 

 its absence from the cat. 



82. Limb Bones. On the left side of the diagram are shown the 

 bones corresponding to the segments already enumerated. 



The proximal segments have each a single bone, the humerus and femur, 

 which are represented as subcylindrical, with enlarged extremities. 



The intermediate segments have each two bones, ulna and radius, tibia 

 and fibula, which, in the normal position of the limbs, lie side by side, the 

 radius and tibia on the cephalic aspect of the limbs, and the ulna and fibula 

 on the caudal. These bones are likewise subcylindrical, but the ulna and 

 tibia are larger at their proximal ends, while the radius and fibula increase 

 more or less distad. The patella (knee-pan) and the olecranon and other 

 special features are not shown. 



