53 



three distal surfaces for the three outer metacarpals are nearly in the 

 same transverse line, which runs parallel with that applied to the os 

 cuneiforme. The dorsal surface is traversed at its outer half by a trans- 

 verse ridge, terminating in a projection between two deep grooves. 



327- The metacarpal bone of the first digit or thumb of the same right fore- 

 foot. It has no distal articular surface for a phalanx, and is the only 

 representative of the rudimental pollex. There are two surfaces at the 

 proximal end, one of which is adapted to the trapezial portion of the 

 scapho-trapezial bone, the other is a larger convex surface, placed nearly 

 at right angles to the preceding, and articulated with the trapezoides and 



the base of the second metacarpal bone. 



* 



328. The metacarpal bone of the third or middle digit of the right fore- 



foot. It is a short thick and strong bone, well adapted to sustain the 

 digit which is armed by the largest claw. The four basal facets of the 

 proximal articular surface are defined by sharp angles ; the middle facet 

 is smooth and concave ; the outer or radial facet is nearly flat, and ex- 

 tends from the dorsal to the palmar aspect of the base ; the ulnar facet 

 meets the middle one at a well-defined angle ; the ulnar side of the base 

 of this metacarpal presents a moderate convexity, upon which the radial 

 half of the base of the fourth metacarpal rests. The under or palmar 

 surface of the shaft of the bone is flattened, and at right angles to the 

 rugged outer and inner surfaces, the radial side is produced at its distal 

 half into an oblong protuberance. The median ridge of the distal articu- 

 lation is slightly concave in the vertical direction : the lateral depressions 

 of the trochlea are very narrow, especially the ulnar one. A surface for 

 a sesamoid bone is extended from the trochlea upon the right side of the 

 under part of the distal joint. 



329. The metacarpal bone of the fourth digit of the right fore-foot. This much 



exceeds the middle metacarpal in length ; its base or proximal end is 

 obliquely extended, and articulates with the middle metacarpal, the unci- 

 form bone, and the fifth metacarpal : the two oblique metacarpal surfaces 

 are nearly parallel, and are separated by well-defined angles from the 



