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toward the volar side of the hand. On the 75th day these bones are 1 mm. 
long and on the 85th day they are 2 mm. long. 
Phalanges, I—The second and third bones of the first row of phalanges 
are present in an embryo 58 days old as two small crescent-shaped bones 
open toward the volar side of the hand. In an embryo two days older four 
of the bones of this row are present. On the 64th day and thereafter all 
five are present. On the 90th day they are 14 mm. long. 
Phalanges, II—The second row are the last of the phalanges to ap- 
pear. On the 75th day the center in the second phalanx is well formed 
and those of the third and fourth phalanges are each represented as two 
very small nuclei, the one on the radial side being a little longer than 
the one on the ulnar side. On the 83d day (N) a single center appears 
in the fifth phalanx. It is crescent-shaped with its closed side outwards, 
and its open side directed towards the radial side of the hand. It retains 
this form, growing only in size in embryos up to 105 days old. At this 
time each of the bones of this row is about half a millimeter long. 
Phalanges, IJ1J.—The first terminal phalanx is the first bone of the 
hand to appear, being present in an embryo of the 56th day. It is club- 
shaped being developed, unlike the rest of the phalanges, in connec- 
tive tissue. Immediately following the appearance of the first terminal 
phalanx the rest of the terminal phalanges appear, the fifth being very 
minute. Lambertz first demonstrated that these bones appear before any 
other bones of the hand, while Rambaud and Renault thought that they 
were the last of the phalanges to develop, and actually picture a hand of 
an embryo with the ossification centers present in the second, but not in 
the terminal row. Bade’s X-ray pictures are too hazy to give any clear 
idea regarding this point. 
OSSIFICATION OF THE BONES OF THE LEG. 
The femur.—tThe ossification center of the femur appears on the 42d 
day and grows gradually, being 1.5 mm. long on the 55th day. On the 
58th day it is 4 mm. long, on the 75th, 8 and on the 85th 15 mm. long. 
Tibia and Fibula—The tibia appears on the 44th day and the fibula 
on the 55th day, at which time the former is about one millimeter long. 
Throughout the early development the tibia remains a little longer than 
the fibula, and about 25% shorter than the femur. 
Iliwm.—The center of the ilium appears a little anterior to its center 
on the 56th day, and by the 58th day it measures 2 mm. in diameter. It 
soon has a knob-like process on its posterior border which often appears as 
a small adjacent nucleus above the great ischiatic notch. By the 85th 
day the antero-posterior length of the center is 6 mm. 
