OSTEOLOGY AND ARTHROLOGY 105 



the same class ; its shaft is more cyHndrical ; its inferior 

 extremity is somewhat thicker. The external rudimentary 

 metatarsal is better developed than the internal ; in the 

 metacarpus the reverse is the case. 



The phalanges so far resemble those of the anterior limb 

 that, as differential characters, we need point out only the 

 following : the first phalanx of the hind-foot is a little 

 shorter than that of the fore-foot ; its inferior extremity 

 is a little narrower, and its superior extremity a little 

 thicker. The second phalanx is a little less expanded 

 laterally. 



The difference in appearance which the three phalanges, 

 anterior and posterior, respectively present are to be borne 

 in mind ; for they are correlated to the general form of the 

 fore and hind feet. We will establish this point when we 

 come to study the hoof (see Figs. loi and 102, p. 257). In 

 •the fore-foot the ungual phalanx has its inferior surface 

 limited externally by a circular border, while the same bone 

 of the hind-foot has this surface a little narrower, more con- 

 cave, and limited by two curved borders which unite 

 anteriorly to form an angle — an arrangement which gives to 

 the general outline of this region the form of the letter V. 



Articulation of the Posterior Limbs 



The Coxo - femoral Articulation. — The head of the 

 femur is received in the cotyloid cavity ; these are the osseous 

 surfaces in contact in this articulation. Thev are main- 

 tained in position by a fibrous capsule and a round ligament. 

 To this latter is found attached, in the horse, a fasciculus 

 which, commencing, as does the round ligament, at the de- 

 pression on the head of the femur, emerges from the cotyloid 

 cavity by the notch which is present in its circumference, 

 and is attached to the anterior border of the pubes, to blend 

 with the tendon of the rectus muscle of the abdomen. This 

 is the pubio-femoral ligament. 



The movements which this joint permits are the same in 

 the quadrupeds as in man, but less extensive. They are : 

 flexion and extension, abduction and adduction, the two 



