3i8 HUMAN ANATOMY. 



are about equal. In the last row the palmar point is at a lower level than the rough- 

 ness that succeeds it. There is a transverse ridge in both on the dorsal aspect for 

 extensor tendons ; the flexor tendons are inserted on the palmar side to a slight 

 ridge on the second phalanx and to a roughness spreading considerably on the shaft 

 of the terminal one. 



Tha phalafiges of the third row are much smaller and flatter than the preceding. 

 The dorsum of the diminutive shaft is convex from side to side and its palmar aspect 

 plane where not encroached upon by roughnesses. The free end is sharp and 

 rounded, with points at each end projecting backward. The dorsal distal border 

 bears a narrow semilunar roughness ; a much broader one on the palmar side sup- 

 ports the pulp of the end of the finger, giving firm attachment to the connective 

 tissue. 



Peculiarities of Individual Phalanges. — Every phalanx of the first row is 

 longer than any of the second row. The first and second phalanges of the middle 

 finger are longer than the corresponding ones of the ring finger, which in turn sur- 

 pass those of the index. Those of the little finger are the smallest. The terminal 

 phalanges are of very nearly the same length. 



The phalanges of the first row have the following peculiarities. That of the 

 index-finger has a very large external tubercle at the dorsum ; the hollow at the base 

 is deeper than that of any other ; the base is relatively strong compared with the shaft, 

 which is flatter than any other. The phalanx of the middle fiyiger is strong in all its 

 parts ; there is a large external tubercle, often divided into a dorsal and a palmar part ; 

 at the distal end the ulnar condyle is more prominent. The phalanx of the ri^ig 

 finger has the base relatively small and the condyles relatively large, so that the 

 borders are nearly parallel ; the dorsum is more convex transversely than that of the 

 third, and much more so than that of the mdex ; it is also narrower. The phalanx 

 of the little finger is weak, narrowing rapidly so as to appear pointed ; there is a 

 tubercle at the inner and dorsal side of the base, and the radial condyle is the more 

 projecting. One cannot, therefore, determine to which side the phalanx of the ring 

 finger belongs. 



In the second ro'w the phalanx of the middle finger is always stronger than 

 that of the ring finger, and the latter than that of the index. According to Pfitzner,^ 

 the distal ends are the more characteristic. In the second finger the radial condyle 

 is the more prominent ; this is also true in the third, but to a less degree ; the ulnar 

 condyle is the larger in the fourth, and still more so in the fifth. 



The distal or terminal phalanges can be distinguished more surely by 

 strength than by length ; the third is the strongest ; then comes the fourth ; next 

 the second, which is more or less pointed ; and last the fifth, which is relatively 

 weak. These characteristics are to be used with great caution in drawing differential 

 deductions. 



Development. — The phalanges have each a centre for the shaft and one for 

 the proximal end. The former appears in the latter half of the third month of fcetal 

 life at about the same time in the terminal and proximal rows. Probably the termi- 

 nal row shows ossification somewhat earlier than the other (Bade). The centres 

 for the second phalanges appear after a distinct interval about the middle of the 

 fourth month. In both the first and second rows the centre appears nearer the 

 proximal end. It is said that in all the rows ossification begins in the middle finger, 

 next in the index, and later in the ring and little fingers ; there is, however, con- 

 siderable variation. The centre for the. second phalanx of the little finger is dis- 

 tinctly later than the others. Ossification begins in the epiphyses in the third year 

 or later. They are fused 'by eighteen. In addition to the proximal epiphyses, the 

 terminal phalanges have each a distal cap-like ossification of perichondria! origin, 

 which quickly joins the shaft. 



Sesamoid bones "^ occur in the metacarpo-phalangeal joints. In the foetus of 

 the fourth month they are very numerous, but many disappear by fusion or other- 

 wise during development. A pair is constant in the joint of the thumb. They are 

 two bones of variable size, in general rather larger than a small pea, lying on the 

 palmar side of the head of the first metacarpal. The tendon of the long flexor passes. 

 'Schwalbe's Morpholog. Arbeiten, Bd. i. and ii., 1893. 



'Ossa sesaraoidea. 



