The Spinal Curvature in an Aboriginal Australian. 493 



the lumbar region, and occupies a place which renders it impossible 

 to associate it either with the curve above or the curve below. 



In the Chimpanzee the first sacral vertebra is brought into associa- 

 tion with the lumbar region by the slight degree of backward incli- 

 nation of the sacrum ; but another factor also comes into play, 

 although to a much less extent, and that is the oblique position of 

 the last lumbar vertebra. 



Let us examine these two factors which exercise so marked an 

 influence in producing this modification of the curvature in the 

 Australian and Chimpanzee spines.. The sacro-vertebral angle can 

 be tested in a variety of ways, but the most convenient method is to 

 prolong the axis lines of the last lumbar and first sacral vertebras, and 

 determine the angle which is formed at the point of intersection. In 

 the spines of five European females the average angle thus obtained 

 was 137 40'. But I am inclined to think that in typical cases the 

 angle in question is not so open. In the young female figured in the 

 text, it is only 117 20' ; whilst in the Australian it was determined 

 to be 141. In the young Chimpanzee, on the other hand, it attains 

 a magnitude of 166. But before coming to a definite decision upon 

 this point, it is well to test the matter in another way. This is 

 rendered necessary by the peculiar position of the last lumbar vertebra 

 in the Australian and also, but to a less degree, in the Chimpanzee. 

 Let us take the axis line of the fourth lumbar vertebra in the human 

 spines, and the third lumbar or corresponding vertebra in the Chim- 

 panzee, and note the angle which is formed by the intersection of this 

 by the axis line of the first sacral vertebra. The angles obtained by 

 this method for the three spines figured are : 



European. Australian. Chimpanzee. 



114 120 C 156 



So far, then, as it is possible to draw a conclusion from one spine, 

 we may say that the sacral obliquity in the Australian is not so 

 marked as in the European. At the same time it is right to state 

 that I have examined individual European spines which exhibited a 

 sacro-vertebral angle as open if not more so than that of the Aus- 

 tralian. In these cases, however, special causes existed for this small 

 degree of sacral obliquity. 



The peculiar position occupied by the last lumbar vertebra in the 

 Australian can be rendered evident by ascertaining the angle which 

 is formed by the intersection of its axis line by the axis line of the 

 fourth lumbar vertebra. The following are the angles thus deter- 

 mined : 



European. Australian. 



173 163 



