OSTEOMETRY; THE MEASUREMENT OF THE BONES 



77 



while there was a marked disparity in the dorsal one, indicating a more 

 definite wedge for the fifth than for the fourth. To get the average 

 difference for a single vertebra these figures are divided by 12, giving for 

 the fourth lumbar vertebra the figures 28 : 26 mm., and for the fifth, 

 28 : 23.4. 



The amount of curvature in a single spine can be indicated by taking 

 the above measurements, adding together the five dorsal thicknesses, 

 and comparing the sum with that obtained by adding the five ventral 

 ones. The result can be best obtained in the form of a General lumbar 

 index, thus : 



39. General lumbar index 



dorsal vertical diam. of lumb. vert. I V X 100 



ventral vertical diam. of lumb. vert. I V 

 The values from this index may be classified as follows : 

 * curtorhachic ( = convex spine) below 98 

 orthorhachic ( = straight spine) 98-102 

 coelorhachic (= hollow spine) 102+ 



The Special lumbar index for a single vertebra may be obtained in a 

 similar way by dividing the dorsal by the ventral antero-ppsterior diame- 

 ter (thickness), and the general index may be calculated from the five 

 results by obtaining the mean, or average, of all five. 



40. Special lumbar index 



dorsal vert. diam. of vert. I, II, III, etc. X 100 

 ventral vert. diam. of same vertebra 



The special index of a given vertebra in a number of cases may be 

 averaged as is done in any other such data, and the results compared as 

 racial criteria. Thus Turner presents the following table. 



From this table there will be noted the marked change of shape of the 

 vertebral bodies from the first to the fifth. In the first and second the 



*Gk. /&<ixts, a spine; Kvpr6s, arched, convex; 6p66s, straight; KofXos, hollow. Turn- 

 er's spelling retained the Greek form, kurtorhachic, coitorhachic, as also in his com- 

 pounds with -kerkic (cercic) below, but the spelling given here is more in accordance 

 with modern usage. 



