221

191

metrical form of the proximal articulation, and from that of the fourth (outer) toe by its
greater length in proportion to its thickness. The form of the proximal articular surface
is given in fig. 3 at II. 1 : the outer half of the surface is most extended from before back-
wards, and its posterior rounded angle is produced, and divided by a groove from the
corresponding part of the inner part of the joint. The under surface of the phalanx
presents a rough tuberosity near each of these angles, and the inner surface of the inner
angle is impressed with a pit for the insertion of the lateral ligament : the under surface
of the middle of the phalanx is flattened : the section of the bone at that part would give
almost a semicircle with the angles rounded off ; but the inner side of the upper convex
part of the phalanx is rather more extended and sloping than the outer one. The distal
articulation is a convex trochlea describing rather more than a semicircle in the vertical
direction, and divided by a wide and deep median channel : the inner moiety of the
trochlea is rather the most produced : on each side of the distal end of the phalanx there
is a depression for the lateral ligament ; it is deepest on the outer side.

The second phalanx of the second toe (II. 2) has its expanded proximal articular
surface divided by a submedian vertical ridge into two concavities, the inner one being
broader in proportion to its vertical extent than the outer one, which shows reverse
proportions : the section of the middle of the shaft is subtriedral with rounded angles ;
the outer and inner sides converging more to the upper surface than in II. 1, and the
inner surface sloping rather more than the outer one : this character distinguishes the
phalanx in question from the corresponding one in the other toes (III. 2 or IV. 2). The
under surface is flattened, the upper one slightly concave lengthwise. The distal
trochlea divided by the vertical wide groove, is more contracted above than in II. 1.
The pits for the lateral ligaments are large and well-marked ; that on the outer side is
the deepest and has a tuberosity beneath it.

The third or ungual phalanx ( II. 3) is three inches in length ; it is figured some-
what foreshortened, being viewed as it is naturally bent in Pl. XLIX. It is a sub-
triedral long cone, bent slightly downwards. The proximal articular surface is
shield-shaped with the base downwards ; it is nearly equally divided by the vertical
ridge which fits into the groove of II. 2: the under surface of the base of the phalanx
presents a broad rough surface for the insertion of the flexor perforans tendon ; the rest
of the under surface is smooth and nearly flat transversely, slightly curved lengthwise.
The lateral surfaces converge to an upper smooth convexity, which near the base of the
phalanx shows the line of insertion of the expanded extensor tendon. The inner surface
is most sloping and most extensive : the upper surface is smooth and convex ; each side
is impressed by a deep vascular groove extending half way towards the apex of the
phalanx. The apex of the claw is pierced by many large vascular canals, for the issue
of the vessels supplying the secreting organ of the powerful claw.

The length of the toe II, as given by the three phalanges, is seven inches and a half.
The length of the proximal phalanx of the middle toe (III.1) is four inches and a half;