The Spinal Curvature in an Aboriginal Australian. 497 



bnt in the European female the summit of the axial curve is placed in 

 the disk, between the third and fourth lumbar vertebras. 



In two particulars, then, the Australian spine resembles the vertebral 

 column of a European male more than that of a European female, 

 viz., in the point of maximum curvature in the lumbar region, and in 

 the fact that the curvature does not include the last dorsal vertebra. 

 The youth of the girl from which it was taken may account for these 

 peculiarities : the spine may not have had time to acquire its special 

 sexual characters, or its full degree of lumbar curvature. 



It is self-evident that when a curve is established in a region where 

 the vertebral bodies are not moulded in accordance with it, the pro- 

 duction of the curvature must be due to the shape of the interver- 

 tebral disks. The difference in height between the anterior, and 

 posterior surfaces of the European lumbar vertebrae (with the excep- 

 tion of the fifth) is so slight that it can have little influence in deter- 

 mining the curve in this region. The difference is to be regarded as 

 the consequence and not as the cause of the curve. The lumbar con- 

 vexity is mainly produced by the intervertebral disks, and when we 

 reflect upon the manner in which the curvature is called into existence,* 

 we can readily understand why this should be so. In the Australian 

 spine the lumbar prominence is produced entirely by the interverte- 

 bral disks. The vertebral bodies, with the single exception of the 

 fifth, are fashioned in a manner unfavourable to the production of a 

 curve of which the convexity is directed forwards. 



The table (pp. 498-9) gives the proportions and indices of the lumbar 

 vertebras and intervertebral disks in the Australian and European 

 spines figured in the text, and also for purposes of comparison the 

 indices of the same parts in four additional European spines. 



The index of the lumbar vertebrae in the Australian girl (101 '4) is 

 low when we consider that for this race the average index is 107'8. 

 But this average has been largely obtained from males, and there is 

 every reason to believe that the index of the female is very consider- 

 ably below this. The four female Australian spines which I measured 

 when preparing my " Cunningham Memoir," gave an average lumbo- 

 vertebral index of 103*1, and of these one had an index of 100*9, and 

 another an index so low as 96' 7. To all intents and purposes, there- 

 fore, the bodies of the lumbar vertebras in the spine of the Australian 

 girl are neutral in so far as the production of a lumbar curve is con- 

 cerned. The intervertebral disks are the parts which determine the 

 curvature, and in conformity with this they present the low index 

 of 49'5. A very special feature in this spine is the small amount of 

 depth exhibited by the lumbar disks posteriorly. It is a character 

 which at once appeals to the eye when the tracing of the mesial 

 section is examined. The two disks which contribute most largely 

 * ' Cunningham Memoir,' No. 2, Roy. Irish Acad., p. 78. 



