76 
THE VOYAGE OF H.M.S. CHALLENGER. 
which the vertical diameters in front and behind were usually equal, whilst the 1st 
lumbar had the anterior diameter 0"4 mm. less than the posterior, and the 5th lumbar had 
the anterior diameter G*2 mm. greater than the posterior. Aeby regards, therefore, the 
change from the concavity of the thoracic part of the spine to the convexity of the lumbar 
to take place at a point between the 2nd and 3rd vertebrae, which opinion is substantially 
corroborated by my observations. It is, therefore, at the two ends of the lumbar series 
of vertebrae that the wedge-shaped form of the bodies is most distinct, the 4th and 5th 
vertebrae having the narrower part of the wedge directed backwards to the spinal canal, 
whilst in the 1st it is directed forwards to the front of the spine. This statement applies 
to the individual vertebrae, both in the black and white races ; but, as in the Australians, 
for example, the upper three lumbars were more constantly deeper behind than in front, 
and the -lower two lumbars were proportionally less thick in front than behind than in 
Europeans, the general effect was to produce, so far as the depth of the vertebral bodies 
themselves and without the intermediate discs can influence the curvature, a lumbar spine, 
in the one race concave forwards, and in the other convex forwards. 
The question now arises, at what period of life do the bodies of the lumbar vertebrae 
assume the wedge-shaped form ? From the measurements, both of Aeby^ and Eavenel,^ 
it would appear that in the new-born child neither the vertebral bodies nor the discs are 
wedge-shaped, and that in all the regions of the spine the anterior and posterior vertical 
diameters are equal, so that the spine, the sacral region being excepted, is almost 
straight. In a boy of three months, measured by Ravenel,^ the lumbar region, including 
apparently both bodies and discs, was 6 mm. higher anteriorly than posteriorly, and in 
one of two years 1 cm. higher. In the spine of a child, apparently in its second year, 
measured by myself, the bodies of the lumbar vertebrae were collectively 4 mm. thicker 
in front than behind, and the half of the increase was in the body of the 5th lumbar. 
It is obvious, therefore, that the anterior vertical diameter of the lumbar region increases 
with the assumption of the erect posture, and with the formation of the convex forward 
curve in the lumbar spine. Some years ago Ravenel measured in Bern the spine in 
twenty-two adult Europeans, eleven of either sex. The mean proportions of the lumbar 
part of the column — the anterior surface of the entire column being estimated as= 100 — 
was in men 30 "5 for the anterior surface of the lumbar spine, and 26*4 for the posterior 
surface; whilst in women it was 31 "9 for the anterior, and only 22'2 for the posterior 
surface. The diff'erence, therefore, for the two sexes was 4'1 in favour of the anterior 
surface in the men, and 9*7 in the women, so that the lumbar spine was considerably 
more convex in the latter sex. Ravenel also stated that in women the posterior surface 
of the whole spinal column was 6 per cent, shorter than in men, which, for the most part, 
1 Der Bau des menschlichen Korpers, Leipzig, 1871, p. 159. Die AltersverscbieJeiilieiten der menschlichen 
Wirbelsaule, Archiv fiir Anatomie, p. 77, 1879. 
2 Die Maasverhaltnisse der Wirbelsaule, Zeitschr. fiir Ariat. und Entwicklungsgeschichte, Bd. ii., 1877. 
3 Op. cit. 
