502 Dr. D. J. Cunningham. 



In the ahove table, I have also introduced the proportions which 

 Aehy gives for the sixteen-year-old girl. It is curious that the Aus- 

 tralian girl should approximate more nearly the adult European 

 female. 



Proportion of Bone and Cartilage in the Lumbar Region of ihe Spine. 

 When the tracings which are reproduced in fig. 1 are closely 

 examined, it becomes apparent that in the lumbar region the constituent 

 elements, viz., the bones and the intervertebral disks, are not present 

 in corresponding proportions in the different spines. The vertical 

 diameters of the bodies of the lumbar vertebrae differ very appre- 

 ciably in the three spines, and with this there is a difference in the 

 thickness of the intervertebral disks. In order that we may the 

 more easily contrast the spines from this point of view, I have 

 formulated an index which may be termed the Sagitto-vertical lumbar 

 index. In calculating this, the sagittal diameter measured from 

 the centre of the posterior face to the centre of the anterior face 

 of the vertebral body is taken as the standard and equaLto 100. 

 The proportion between this diameter and the vertical diameter, 

 measured from the centre of the upper surface to the centre of the 

 lower surface of the vertebral body, can thus be readily expressed. 

 A high index will indicate a long vertebral body ; a low index, on 

 the other hand, will indicate a short vertebral body. In the table 

 which follows I have introduced the Baboon, Macaque, and Orang, 

 with the view of enabling us to decide whether or not the difference 

 exhibited in the sagitto- vertical lumbar index of the European, 

 Australian, and Chimpanzee is one from which any important deduc- 

 tion may be drawn. 



Two points are rendered very manifest by the above figures, viz., 

 (1), that there is a rapid and decided increase in the length of the 

 lumbar vertebral bodies as we pass from the European, through the 

 Australian, Chimpanzee, and Baboon to the Macaque ; and (2), that 

 as the bones elongate the cartilaginous disks become shortened. 



The difference in relative length of the lumbar vertebrae in the 

 European and Australian is very marked, the sagitto- vertical index of 

 the former being 80'9, and of the latter 87*0. It must be borne in 

 mind, however, that I have only had an opportunity of examining 

 the one Australian.* Again, it is remarkable that the Orang in the 

 height of its vertebrae should show such a decided deviation from 

 other Apes, and approach so closely to Man. A mesial section through 

 the Orang renders this character apparent to the eye/j" 



In estimating the vertical depth of both vertebral bodies and inter- 



* There "are striking sexual differences in this respect,. In the male, the bodies 

 of the vertebrse are more compressed. Eight skeletons of female Andaman Islanders 

 afforded a sagitto-vertical lumbar inde$ of 90*4. 



f ' Cunningham Memoir,' No. 2, Plate III, Royal Irish Academy. 



