68 
THE VOYAGE OF H.M.S. CHALLENGER. 
the lumbar curve which he has recently published has given the mean lumbar indices in 
seventy-six European skeletons, the general results of which accord very closely 
with those which I have obtained from my more limited number of skeletons. The 
mean index in his series was 95 "8, and the mean index of the individual vertebrse 
ranged from 106*1 for the 1st lumbar to 81 "6 for the 5th. He also pointed out that 
the two sexes differed in the jDroportional depth of the anterior and posterior surfaces 
of the bodies of the lumbar vertebrae, so that they did not have the same mean 
lumbar index. The average in twenty-one Irish men he found to be 96 "2, and in twenty- 
three Irish women 93*5, from which it is evident that in the women the anterior vertical 
diameter of the five lumbar bodies collectively was proportionally greater than in the 
men, and the lumbar spine in them was more convex. 
During the past few years I have collected the skeletons of seven adult aboriginal 
Austrahans — six men and one woman. In four of the men the lumbar spine is 
complete, in one the last lumbar vertebra has been lost, in another the 3rd, 4th and 5th 
lumbars are absent ; in the woman all the lumbars are present. In each of the five 
skeletons in which the lumbar spine was complete, the vertical diameter of the bodies 
of the five vertebrae collectively was deeper behind than in front ; the maximum 
difierence observed in three male skeletons was 9 mm., the minimum in the woman was 
2 mm. The mean collective depth of the five vertebrae in the five perfect Australian 
skeletons was 112*2 mm. for the anterior surface of the bodies, and 118'8 mm. for the 
posterior surface ; the mean diff'erence, therefore, was 6"6 mm. in favour of the 
posterior surface. In the skeleton in which the 5th lumbar w^as absent the collective 
diameter of the four lumbars was 3 mm. greater behind than in front. In the relation 
of the vertical diameter of the posterior surface to the anterior surface the opposite con- 
dition prevailed to that which was found in the Europeans. Before, indeed, I had 
measured the vertebrae in these Australians, I found that, when the bodies of the lumbar 
vertebrae in each spine were placed in apposition with each other, without the interposi- 
tion of artificial discs, they produced a concave curve forward, and not a convex curve 
as in the European spine, so that I was not surprised to see, when the bodies were 
measured, that collectively they were deeper posteriorly than anteriorly. 
When the measurements of the individual lumbar vertebrae in the series of Australian 
spines were compared, it was seen that the body of the 1st lumbar vertebra in every 
instance was deeper behind than in front, in four skeletons as much as 4 mm. The 
body of the 2nd lumbar was with one exception deeper behind than in front, in two 
specimens as much as 4 mm. ; in the exceptional vertebra the depth in front was 1 mm. 
greater than behind. The body of the 3rd lumbar in four skeletons was deeper behind 
than in front ; in one skeleton they were equal, and in another — the adult female — the 
anterior diameter was 1 mm. deeper than the posterior. The body of the 4th lumbar 
was deeper behind than in front in three skeletons ; these diameters were equal in one, 
