OSTEOMETRY; THE MEASUREMENT OF THE BONES 97 



Simian apes: 



Gibbon (4) 88 75 



Orang (11) 95 81 



Gorilla (5) 101 77 



Chimpanzee (2) 120 73 



Lower apes 165 153.9 



Lemurs 120 138 



V. SHAPE OF THE SHAFT 



Through the formation of longitudinal ridges the shaft of the ulna 

 becomes more or less definitely a three sided prism, one edge of which, the 

 one turned towards the radius, forms a sharp crest, often considerably 

 developed. Aside from these there are many minor elevations and slight 

 depressions, which have their meaning for the anatomist in relation to the 

 attachment of muscles, but in which thus far no racial characters have 

 been established, and it is more probable that the variations are mainly 

 those of age, sex, and degree of muscular development. 



Two methods have been devised, however, for determining the shape of 

 the shaft at different levels, the one mechanical, the other mathematical. 

 The first consists of surrounding the shaft at a given level with a band of 

 wax, which, when removed, gives the exact form of the part enclosed. 

 For this a mixture of wax and paraffin, 4 : 1, is warmed to the degree 

 necessary to make it plastic, worked a little between the fingers, and then 

 pressed around the region selected in the form of a band. The upper 

 and lower margins of this band are then made straight by means of a 

 knife, and the whole is then plunged into cold water to harden. When 

 sufficiently hard the ring is cut across at two opposite points and the two 

 halves are removed quickly from the bone and dropped upon a table or 

 board without being handled. They are then placed together and fast- 

 ened by means of a hot spatula applied to the outer surfaces. In this way 

 may be obtained the outlines of any section, but the two points of greatest 

 interest are (1) the point of greatest crest development, and (2) the cylin- 

 drical region above the distal epiphysis, where the ridges fail and the cali- 

 ber is the minimum. 



The second method is the more usual one of obtaining an index from 

 two diameters taken at the same level and at right angles to each other. 

 For this the point of greatest crest development is recommended, a point 

 at about the upper third of the bone. Fischer uses for the two diameters 

 the dorso-volar, from the ridge on the dorsal side to the flat plane on the 

 ventral, and the transverse, exactly at right angles to the first. His 

 index is formed by dividing the first by the second, or, in other words, by 

 considering the transverse diameter = 100. Since in most ulnae the 

 shape of a cross-section at this place is triangular, there are obvious 

 difficulties in establishing two diameters at right angles to each other, 

 while a measurement that includes the crest would give, not the primary 

 shape of the bone, but the degree of development of the crest itself, that 



