The material consists of 141 Japanese embry-os ( _??_ 78, _??_ 59), which lengths range from 10 mm to 51 cm. The spinal cords of these embryos were opened from back, their heights projected to the vertebral column. The vertebral heights were defined through their transverse process, as one can see in Fig.1.
The lengths of our embryos at the end of ea-ch month are as follows.
1M, 7mm (C-R), 2M, 3cm (C-R),
3M, 8cm (total or C-H), 4M, 16cm
5M 24cm, 6M 29cm, 7M 34cm, 8M 39cm,
9M 44cm, 10M 51cm
By the first month embryos are the caudal ends of the spinal cords beyond those of the vertebral columns, in the early 2nd month they move higher to the same level of those of the vertebral columns and at the end of the same month they are in the level of the upper part of the coccygeal vertebrae. During 3rd month they remain to the level of the caudal part of the sacral vertebrae and in the 4th they move from the caudal to the cranial part of the sacral canal. By almost all 5 month old embryos are the caudal ends of the spinal cord out of the sacral canal and in the level of the lower, lumbal vertebrae. (By 17 embryos of this month from L₃ to L₅, only by 3 S₁) Then they move in the 6th month from L₅ to L_4-5, in the 7th to L₄, in the 8th to L_3-4 in the 9th and 10th to L₃.
To see the sexual difference about the heights of the caudal ends were 46 male and 48 female embryos available, by which among 20cm unit 13 were male and 7 female higher, so that the male seems to have higher caudal ends than the female.
The percentage of the length of the spinal cord to that of the vertebral column is 96.30 by the 2nd, 97.23 by the 3rd, 86.08 by the 4th, 80.34 by the 5th, and 74.20, 71.38, 75.75, 69.53 and 68.68 respectively from the 6 th to 10 th month. So is the correlative change between spinal cord and vertebral column most remarkable from 3rd to 4th month, then from 4 th to 5th. The same percentage of the adult is after Uenae 61.4 in the male, 62.8 in the female.
The sagittal and transverse diameters of the spinal cords are larger at the cervical swelling than at the lumbal in the 3rd month, from the 4th month upward those of the lumbar larger than those of the cervical.
The form-of the conus can be classified in 2, one sloping gradually, the other abruptly ; the latter is only in 21% to be seen.
The filum terminale is from the 4th month onward distinguishable with naked eye and from
4th to 7th is the Filum terminale externum a little longer than the F. t. internum, from 8th to 10th become their correlation reverse. At termin is the Filum terminale internum ca 3 cm long, externum ca 2 cm. After Uenae is their length correation by the adult. 2 : 1, while by our new born 3 : 2.
Among the elder from 4th to 10th month 122 embryos there are rudimentary spinal ganglion along the conus and filum terminale in 32 cases (26.2%), They measure about 0.5 mm or lesser, their number ranges from 1 to 7. When they are extremely rudimentary, they consist of only several ganglien cells. These rudimentary ganglions have regularly prae-and postganglional nerve fiber bundles.

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