osteometry; the measurement of the bones 



117 



of the promo ntorium to that of the apex, without including the coccyx. 

 (Fig. 37, the curved line adb). TM. 



2. Mid-ventral straight length (length of sacral axis); the length of 

 the straight line drawn between the two terminals employed in the pre- 

 vious measurement (the line ab in Fig. 37). SC. 



3. Anterior curved breadth; the length of the line drawn perpendicular 

 to (1), across the ventral surface of the first sacral vertebra, between 

 the widest points of the margins of the lateral wings. TM. 



4. Anterior straight breadth; the length of the straight line drawn 

 between the two termini employed in (3). SC. 



5. Middle curved breadth; the 



length of the line drawn perpendicular y f 



to (1), across the ventral surface, 



connecting the posterior angles of the 



wings as termini. These terminal 



points are practically at the level 



of the lowest point of the auricular 



surfaces, which can be used in cases 



where the lower angles of the wings 



are indefinite. TM. 



6. Middle straight breadth; the 

 straight line drawn between the 

 termini employed in (5). SC. - 



7. Lower breadth; the distance be- 

 tween the posterior lateral angles, or, 

 when these are not evident, the 

 greatest breadth across the bone at 

 the level of the most posterior pair of 

 foramina. At this level the ventral 

 surface of the bone is so flat that there 

 is practically no difference between the 

 straight and curved breadths. SC. 



8. Maximum height of curvature; the greatest distance between the two 

 lines used in (1) and (2), measured on a line perpendicular with (2); 

 i.e., the line cd in Fig. 37. 



9. Position of the maximum height line; the relative position of the 

 point c in Fig. 37, the foot of the perpendicular used in the previous 

 measurement. The distance here measured is that from the promontor- 

 ium to the foot of the perpendicular, the line ac of the figure above 

 referred to. This figure is a profile projection of the median sagittal 

 curve, and is drawn upon a properly oriented bone by means of a diagraph, 

 precisely as in the corresponding craniogram described elsewhere. 

 Several important sacral measurements may be measured upon it, such 

 as Nos. 2, 8, and 9. These may be measured also directly upon the bone, 

 and the two used to check each other. An instrument especially devised 



Fig. 37. — Median curve of sacrum. 

 I-V, centra of vertebrae; a-b. mid-ventral 

 curved length; c-d. maximum height of 

 curvature. (After Radlauer) 



