20,1 Yap and Pineda: Two Cases of Ectrosyndactyly 5 
There is a Y-shaped cleft, extending to the metatarsal region, 
between the great and the fourth toes. 
The tarsal bones are distinct except the cuneiform bones which 
do not show clearly in the picture. (Plate 5, figs. 1, 2.) 
The metatarsals are all present. All are normal except the 
second and third; the second is smaller and curves to the right, 
and the third is slender and is longer due to fusion with the prox- 
imal phalanx which is rudimentary. 
The phalanges of the first are normal; the second has no pha- 
langes; the third has only the rudimentary proximal phalanx 
fused with its distal end; the fourth has a longer proximal pha- 
lanx and a shorter middle one, while the distal is normal. The 
phalanges of the last toe are normal except for the absence of 
the middle one; however, this may be fused with the distal 
phalanx, the base of which appears rather large. (Plate 6.) 
DISCUSSION 
In these two cases two interesting facts are prominent. First, 
that neither woman experienced any inconvenience in the per- 
formance of her daily duties; and second, that there is no history 
of such deformity in the other members of their families. 
In this connection it is probably convenient to give a brief 
review of the embryological development of the skeletal parts 
of the two human extremities, especially as regards the meta- 
_ carpals, metatarsals, and phalanges. According to Keibel and 
Mall and to Minot at about the third week of embryonic life the 
limb buds appear, formed by’ the condensation of the mesen- 
chyme into scleroblastema. Between the fifth and sixth weeks, 
when the embryo has attained 11 millimeters in length, the hand 
and foot plates are differentiated; the digital rays appear as 
bars of scleroblastema, but they are not differentiated into meta- 
carpals, metatarsals, and phalanges until the chondrogenous 
period. Later, chondrification centers appear, those of the 
metacarpals, metatarsals, and phalanges appearing before those 
of the carpals and tarsals. By the middle of the third month 
the cartilages of the hand and foot have acquired the adult shape. 
Ossification of the shafts of the metacarpals and metatarsals 
begins at the eighth or ninth week and that of the phalanges 
at the ninth or tenth week. The epiphyses of the metacarpals 
and metatarsals ossify from the third to the eighth year, and 
their union is accomplished at the eighteenth to the twentieth 
year. Epiphyseal ossification of the phalanges begins from the 
