_a_, Cranium; _b_, face; _c_, mandible; _1H-7H_, cervical vertebræ; _13B_, last thoracic vertebra; _1L-7L_, lumbar vertebræ; _K_, sacrum; _S_, coccygeal vertebræ; _1R-13R_, ribs; _R.Kn._, costal cartilages; _St._, sternum; _d_, scapula; _d′_, supraspinous fossa; _d″_, infraspinous fossa; _1_, spine of scapula; _2_, acromion; _3_, tuberosity of scapula; _3′_, articular end of scapula; _e_, humerus; _4_, head of humerus; _5_, external tuberosity of humerus; _5′_, deltoid ridge; _6_, _6′_, epicondyles of humerus; _7_, external condyloid crest; _7′_, coronoid fossa; _f_, radius; _g_, ulna; _8_, olecranon; _9_, “beak” of ulna; _h_, carpus; _i_, metacarpus; _k_, proximal phalanges; _l_, middle phalanges; _m_, distal phalanges; _n_, sesamoid; _p_, ilium; _10_, wing of ilium; _11_, shaft of ilium; _12_, crest of ilium; _13_, external angle of ilium (tuber coxæ); _14_, internal angle of ilium (tuber sacrale); _15_, superior ischiatic spine; _q_, pubis; _r_, ischium; _16_, tuber ischii; _17_, acetabulum; _s_, femur; _18_, head of femur; _19_, trochanter major; _20_, trochanter minor; _21_, trochanter tertius; _22_, _23_, condyles; _24_, _25_, epicondyles; _26_, trochlea; _t_, patella; _u_, tibia; _27_, tuberosity of tibia; _28_, _29_, condyles of tibia; _30_, internal malleolus; _v_, fibula; _31_, external malleolus; _32_, head of fibula; _w_, tarsus; _x_, metatarsus; _y_, phalanges; _33_, occipital bone; _34_, paramastoid (styloid) process; _35_, parietal bone; _36_, frontal bone; _37_, lacrimal bone; _38_, malar bone; _39_, squamous temporal; _40_, maxilla; _40′_, infraorbital foramen; _41_, premaxilla; _42_, nasal bone; _43_, external auditory meatus; _44_, canine tooth; _45_, masseteric fossa; _46_, angular process of mandible. (After Ellenberger, in Leisering’s Atlas.) ] The =sacrum= results from the early fusion of three vertebræ. It is short, wide, and quadrangular. The spines are fused to form a median crest, which is notched, however, between the summits of the spines. On either side are two tubercles, vestiges of the fused articular processes. The pelvic surface is deeply concave and presents two pairs of foramina. The wings are prismatic and very high. Their lateral surfaces are extensive, face almost directly outward, and bear an auricular surface on the lower part. The anterior surface of the body of the first vertebra is extensive, depressed in its middle, and bears a prominent lip below. The anterior articular processes are large and have extensive, slightly concave facets which face upward and inward. The posterior articular processes are small. The transverse processes of the last vertebra project backward and may articulate or fuse with those of the first coccygeal. The sacral canal is strongly compressed dorso-ventrally. [Illustration: FIG. 116.—ATLAS OF DOG, VIEWED FROM ABOVE AND BEHIND.