BONES OF THE PELVIC LIMB 



165 



is almost four-sided, in the second and fifth three-sided, in the first rounded. 

 The proximal ends (Bases) articulate with each other and with the corresponding 

 carpal bones. The carpal articular surface formed by them is concave from side 

 to side, convex from before backward. The distal ends (Capitula) have articular 

 surfaces of the nature of a head, but bear a sagittal ridge behind, except the first, 

 which is grooved. 



The five digits have three phalanges each, except the first, which has two. 

 The third and fourth digits are the longest; the first is very short and does not come 

 in contact with the ground in walking. The first phalanges of the chief digits 

 have four-sided shafts, which are slightly curved forward. The proximal end 

 of each has a concave surface for articulation with the metacarpal bone and is 

 deeply notched behind. The distal end has a trochlea for articulation with the 

 second phalanx, and lateral depressions for ligamentous attachment. The 

 second phalanges are aljout two-thirds of the length of the first phalanges. 

 The proximal articular surface consists of two cavities separ- 

 ated by a sagittal ridge. The distal extremity is wider and 

 flatter than that of the first. The third phalanges correspond 

 in general to the form of the claws. The base has an articu- 

 lar surface adapted to the second phalanx and is encircled 

 by a collar of bone. The volar surface bears a wing or tuber- 

 osity, and on either side of this is a foramen. The ungual 

 part is a curved rod with a blunt-pointed free end. It is 

 rough and jiorous. Its base forms with the collar previously 

 mentioned a deep groove, into which the proximal border of 

 the claw is received. The two phalanges of the first digit 

 resemble in arrangement the first and third phalanges of the 

 other digits. 



Nine volar sesamoids are usually present. Two are 

 found at each metacarpo-phalangeal joint of the chief digits. 

 They are high and narrow, articulate with the distal end of 

 the metacarpal bone in front, and have a small facet on the 

 base for the first phalanx. On this joint of the first digit 

 there is usually a single flattened sesamoid, but exceptionally 

 two are present. The distal volar sesamoids remain cartila- 

 ginous. A nodular dorsal sesamoid occurs in the anterior 

 part of the capsule of the metacarpo-phalangeal joints, 

 and cartilaginous nodules are found in a similar position 

 the joints between the first and second phalanges. 



Fig. 133. — Second and 

 Third Phalanges 

 OF Dog. 



a, Wing of third 

 phalanx; b, coronary ridge; 

 C foramen for digital ar- 

 tery; d, ungual surface of 

 third jjhalanx; e, .second 

 phalanx; /, fir.st phalanx; 

 g. ela.stic dorsal ligaments. 

 (From Leisering's Atlas.) 



in connection with 



BONES OF THE PELVIC LIMB 



The ilium is nearly parallel with the median plane and its axis is only slightly 

 oblique with regard to the horizontal plane. The gluteal surface is concave. The 

 IKac surface is almost flat. The auricular surface faces almost directly inward, 

 and in front of it there is an extensive rough area. The ilio-pectineal line is very 

 distinct and is uninterrupted. The anterior border or crest is strongly convex, 

 thick, and rough. The internal angle is represented by a thickened part which 

 bears two eminences, homologous with the posterior superior and posterior inferior 

 iliac spines of man. The external angle also has two prominences, which are 

 equivalent to the two anterior spines present in man. The shaft is almost sagittal 

 and is compressed laterally. Above it is smooth and rounded, and below it bears a 

 crest externally which terminates at a tuberosity in front of the acetabulum. 



The ischium has a twisted appearance owing to the fact that its acetabular 

 part is nearly sagittal while the posterior part is almost horizontal. The two bones 



