148 SKELETON OF THE PIG 



The third and fourth metacarpals are flattened from before backward, three-sided, and 

 placed close together. The distal end of each bears a trochlea for articulation with the first 

 phalanx and the sesamoids. The third is the wider of the two, and articulates with all of the 

 lower row of the carpus except the first. The fourth articulates with the fourth carpal chiefly, 

 but has a small facet for the third. The second and fifth metacarpals are placed further back 

 than the chief bones. The fifth is considerably the thicker of the two. The proximal ends are 

 small and articulate with the corresponding carpal and metacarpal bones. The distal end is 

 relatively large; its articular surface is condyloid in front, trochlear behind. 



Each chief digit comprises three phalanges and three sesamoids. The bones 

 of the chief digits resemble those of the ox in form, but there is no foramen on the 

 interdigital side of the extensor process and the proximal sesamoids are narrow and 

 ridged behind. The phalanges of the accessory digits (which do not reach the 

 ground ordinarily) are similar in form but much smaller. 



BONES OF THE PELVIC LIMB 



The OS coxae is long and narrow. The ilium and ischium are almost in line 

 with each other and sagittal in direction. The wing of the ilium bends outward 

 much less than in the horse or ox. The gluteal surface is divided into two fossse 

 by a ridge, which is continuous with the superior ischiatic spine behind. The 

 inner surface presents an extensive rough area behind, which is in apposition with 

 the wing of the sacrum. The smooth iliac area is narrow, and is bounded above 

 by a ridge. The crest or anterior border is convex, and is thick, rough, and prom- 

 inent in'its middle, which forms the highest point of the bone. The internal angle 

 is lower than the crest, is directed backward, and articulates internally with the 

 sacrum. The external angle is lower still and is very little thickened. The 

 ischia in the female are somewhat divergent and flattened behind. The tubera 

 are everted and bear three prominences. There is a crest or tuberosity on the 

 ventral surface. The superior ischiatic spine is like that of the cow, but is slightly 

 incurved and the muscular ridges on its outer face are more pronounced. The 

 symphyseal part of the pubis is thick and the two bones are almost in a horizontal 

 plane. The ilio-pectineal eminence is prominent and the psoas tubercle is well 

 marked. 



The acetabulum is placed a little further back than in the ox. The rim is 

 thick and is cut into posteriorly by a narrow fissure, which leads into the deep fossa 

 acetabuli. The three pieces of the os coxae are fused by the end of the first year, 

 but the crest and the ischial tul^era are partially separate till the sixth or seventh 

 year. The symphysis does not usually undergo complete anchylosis. Interischial 

 bones are present. 



The inlet of the pelvis is elliptical and very oblique. In a sow of full size the 

 conjugate diameter is about five to six inches (10 to 12 cm.) and the transverse 

 about three and a half to four inches (ca. 8.75 to 10 cm.). In the female the floor 

 is relatively wide and flattened, especially at the outlet, where the tubera are 

 everted; it also has a decided downward inclination behind. The pelvic axis 

 is therefore correspondingly oblique. The ischial arch is wide. In the boar the 

 pubis is much thicker and the ischia are not everted posteriorly. The inlet is 

 smaller. The floor is concave from side to side and slopes decidedly less than in 

 the sow. The superior ischiatic spines are more incurved, and the ischial arch is 

 much narrower and deeper. 



The femur has a relatively wide and massive shaft, on which four surfaces might 

 be recognized. The principal nutrient foramen is situated in the proximal third 

 of the anterior surface. The posterior surface is wide, and is limited outwardly 

 by a ridge which extends from the trochanter major to the large external supra- 

 condyloid crest. There is no supracondyloid (plantar) fossa. The head is strongly 

 curved, and is marked toward the inner side by a rather large depression for the 



