40 INTRODUCTION. 



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

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

 difficulty with the arras 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 keejaing 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 segmenta, con- 

 nected with each other and with the soma by three artlira (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 

 hrachium (upjDcr arm) and meros (thigh). The intermediate segments are 

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

 maniis (hand) and^es (foot). 



The entire limbs are joined with the trunk by the shoiclder and Jiip 

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

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

 brachium and manus, the crus and j^es respectively. 



The teclinioa] names for tlie artlira placed in parenthesis are those wliicli were pro- 

 posed ill 1873 by tlie 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 pi'oxiinal 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, nlna and radius, tibia 

 awd 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, Avhile the radius and fibula increase 

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

 special features are not shown. 



