BONES OF THE PELVIC LIMB 131 



Each has four surfaces. The tlorsal or wall surface is marked in its lower part by a 

 shallow groove, along which there are several foramina of considerable size; the 

 posterior one of the series is the largest, and conducts to a canal in the interior of 

 the bone. Below the groove the surface is prominent, rough, and porous. Near 

 and on the extensor process are several relatively large foramina. The slope of the 

 surface is very steep posteriorly, but in front it forms an angle of 25 to 30 degrees 

 with the ground plane. The articular surface is narrow from side to side, and 

 slopes downward and backward. It is also oblique transversely, the interdigital 

 side being the lower. It is adapted to the distal surface of the second phalanx, with 

 the exception of a facet behind for the distal sesamoid. The extensor process is 

 very rough. The volar or sole surface is narrow and slightly concave, and presents 

 two or three foramina of considerable size. It is separated from the wall surface 

 by a border which is sharp in front, rounded behind. There is no semilunar cre^st, 

 since the deep flexor tendon is attached to the thick posterior border of the sole 

 surface. The interdigital surface is smooth and grooved below, rough and porous 

 above. At the upper angle it is perforated by a large foramen, which is equivalent 

 to the volar foramen of the horse and leads to a cavity in the middle of the bone. 

 The surface is separated by a rounded border from the wall surface, and by a sharp 

 edge from the sole surface. The wing or angle is very short and blunt, and there 

 is no lateral cartilage. 



Four proximal sesamoids are present, two for each digit. They are much 

 smaller than in the horse. The bones of each pair articulate with the correspond- 

 ing part of the distal end of the large metacarpal bone by their anterior surfaces, 

 with each other and with the first phalanx by small facets. 



The two distal sesamoids are short and their ends are but little narrower than 

 the middle. 



BONES OF THE PELVIC LIMB 



The ilia are almost parallel to each other and are also less oblique with regard 

 to the horizontal plane than in the horse. They are relatively small. The gluteal 

 line is prominent and is nearly parallel to the external border; it joins the superior 

 ischiatic spine. A rounded ridge separates the two parts of the ventral surface. 

 The surface for articulation with the sacrum is triangular. The internal angle is 

 truncated, does not extend as high as the vertebral spines, and is separated from 

 the opposite angle by a wider interval than in the horse. The external angle is 

 relatively large and prominent ; it is not so oblique as in the horse, and is wide in 

 the middle, smaller at either end. The shaft is short and compressed from side 

 to side. 



The ischium is large. Its long axis is directed obliquely upward and back- 

 ward, forming an angle of about 45 to 50 degrees with the horizontal plane. The 

 transverse axis is oblique downward and inward at a similar angle, so that this 

 part of the pelvic floor is deeply concave from side to side. The middle of the 

 ventral surface bears a rough ridge or imprint for muscular attachment. The 

 superior ischiatic spine is high and thin, and bears a series of almost vertical rough 

 lines externally. The tuber ischii is large and three-sided, bearing upper, lowTr, 

 and external tuberosities. The ischial arch is narrow and deep. The symphysis 

 bears a ventral ridge, which fades out near the ischial arch. 



The acetabular branch of the pubis is narrow, and is directed outward and a 

 little forward. The anterior border is marked by a transverse groove which ends 

 below the rough ilio-pectineal eminence. The longitudinal branch is wide and 

 thin. 



The acetabulum is smaller than in the horse. The rim is rounded and is 

 usually marked by two notches. One of these is postero-internal and is narrow 

 and deep ; it leads to the deep acetabular fossa and is commonly almost converted 



