INTRODUCTION 



11 



and among edentates two joints may be fused. Among the bats the 

 metacarpals and phalanges are enormously elongated to furnish supports for 

 the wing-membrane. The terminal phalanges vary greatly and are enclosed 

 or protected in front by nails, hoofs or claws. Often, on the palmar side of 

 the hand, opposite the articulation between the metacarpus and first phalanx, 

 paired semilunar, sesamoid bones are developed in the connective tissue of 

 the region. 



The pelvis (Fig. 11) of either side consists of three bones which all meet 

 in the articular cup (acetabulum) for the femur, the three bones, ilium (il), 

 ischium (is), and pubis (pb), being independent in youth but 

 usually fusing in the adult to make the innominate bone. The 

 two innominate bones meet in the median ventral line, making 

 the symphysis. The pubis and ischium expand along this 

 symphysis, finally meeting and enclosing between them the 

 obturator foramen (fo), which is in life closed with connective 

 tissue and muscle. 



The thigh bone or femur (Fig. 12) is 

 usually a long cylindrical bone, the ball-like 

 head of which is separated from the shaft 

 proper by a constricted neck. Opposite the 

 head, on the outer and back side of the femur, 

 projects the greater 

 trochanter (tr.^) for 

 muscular attach- 

 ments, and separated 

 off by a shallow to 

 deep depression, the 

 digital fossa. On the 

 front and inner side 

 of the bone, just 

 the head, 

 the smaller 

 lesser tro- 

 (tr:^). A 

 trochanter 

 may occur on the 

 hind border of the 

 shaft below the 

 greater trochanter, 

 and at some distance 



below 



occurs 



conical 



chanter 



third 



Kight iniioininate bone of 

 the dog, seen from in front. 

 ... il, Ilium ; ph, pubis ; is, 



from it ; it is present ischium ; a, acetabulum ; fo, 

 -. • foramen obtnratorium : s, 



in many primitive symphysis. 



Fig. 12. 



Right femur of the dog 

 (posterior aspect). c, 

 Condyle; <r.i, larger, and 

 tr.^, smaller trochanter ; 

 ci, inner articular surface 

 (entocondylus) ; ca, outer 

 articular surface ; /, fossa 

 intereondyloidea. 



Left tibia (0 and 

 fibula (fl) together 

 with patella (pa) of 

 the dog, seen from 

 in front, c, Upper 

 articular surface ; g, 

 lower articular sur- 

 face of the tibia ; en, 

 procnemial ridge; mi, 

 malleus internus ; co, 

 lower facet of the 

 fibula. 



placentals, including 



many ungulates, rodents, insectivores and edentates. The distal end of the 



femur is greatly thickened, narrow in front, but expanding behind, with two 



rounded articular facets, the ectocondyle (ca) and entocondyle (ci), separated 



by the intercondylar groove (/), and each bounded externally by a prominent 



ridge. 



The thick upper end of the tibia (Fig. 13) forms a triangular, slightly 

 depressed articular facet (c), separated into two surfaces by a median bifid 



