1887 | Variation of the Human Shoulder-Blade. 627 
THE RANGE OF VARIATION OF THE HUMAN 
SHOULDER-BLADE. 
BY THOMAS DWIGHT, M.D." 
HE late Professor Broca read a paper before La Société 
d’Anthropologie in 1878? in which he described the scapular 
and the infra-spinous indices, and proposed them ase methods of 
ethnological research. Briefly stated, the scapular index is the 
proportion of the breadth of the scapula, measured along the 
base of the spine, to the length, the latter being considered one 
hundred. The infra-spinous index is the proportion of the 
breadth to the length of the infra-spinous fossa, the latter being 
considered one hundred. 
The human scapula being the starting-point, Broca under- 
stands by “length” the line connecting the highest and lowest 
points, although in almost all mammals this is not the longest 
dimension. The line showing the breadth being called AB and 
that of the length CD, the index is obtained by calculating 
100 X AB 
CD 
border of the scapula, but runs some distance before it. The 
line AD. representing the infra-spinous length runs from the 
posterior end of AB to the lower end of CD. The infra- 
‘ x - ` 100X AB 
spinous index is represented by the fraction x . Professor 
The length very rarely coincides with the posterior 
Broca used these indices both in comparative anatomy and in 
the study of characteristics of race, sex, and age in man. 
- In all orders of mammals, with one exception, the scapular 
index is greater than in man. In quadrupeds it is evident that 
the long diameter of the bone should at least approximately 
coincide with the line of pressure, and consequently we find the - 
‘breadth—z.c, the line along the base of the spine—the longer. In 
erect man, with his great range of movement of the anterior ex- 
tremities, there is need of greater leverage for the movements of 7 
the scapula, and less need of resistance to pressure, so we find a 
long and narrow scapula. This condition is approached in the 
- anthropoid apes, and even surpassed in the bats, who have a — 
‘z Parkman Professor of Anatomy at Harvard University. 
7 2 Bulletins de la Société ď’Anthropologie de Paris, série 3, tome i. a 
_ 3 By a most unfortunate oversight the AB and AD are transposed in Broca’s paper. 
