288 OSTEOLOGY. 



Following the convenient method of division adopted with other indices, the dental indices 

 may be divided into three series, called respectively 



Microdont, index below 42 : including the so-called Caucasian or white races. 

 Mesodont, index between 42 and 44 : including the Mongolian or yellow races. 

 Megadont, index above 44 : comprising the black races, including the Australians. 



Many complicated instruments have been devised to take the various measurements required, 

 but for all practical purposes the calipers designed by Flower or the compas glissitre of Broca are 

 sufficient. 



As an aid to calculating the indices, the tables published in the Osteological Catalogue of the 

 Royal College of Surgeons of England, Part I., Man; Index -Tabellen zum anthropometrischen 

 Gebrauche, C. M. Furst, Jena, 1902 ; or the index calculator invented by Waterston will be found 

 of much service in saving time. 



(2) Indices and Measurements of other Parts of the Skeleton. 



In addition to the indices employed to express the proportions of the cranial measurements, 

 there are others similarly made use of to convey an idea of the proportions of different parts of 

 the skeleton. Of these the following may be mentioned as those in most common use : 



Scapula. At birth the form of the human scapula more closely resembles the mammalian 

 type in that its breadth, measured from the glenoid cavity to the vertebral border, is greater in 

 comparison with its length than in the adult. This proportion is expressed as follows : 



Breadth from glenoid cavity to vertebral border x 100 ~ 



, . J . . . . . = Scapular index. 



Length irom medial to inferior angle 



The index ranges from 87 in African pygmies, which therefore have proportionately broader 

 scapulae, to 61 in Eskimos. The average European index is about 65. 



Hip Bone. The relation of the breadth of this bone to its height is computed as 

 follows : 



Iliac breadth x 100 



Ischio-iliac height 



= Innominate index. 



Man as compared with the apes is distinguished by possessing proportionately broader and 

 shorter hip bones. The index in man ranges from 74 to 90. 



Pelvis. The form of the human pelvis is characterised by an increased proportionate width 

 and a reduced proportionate height or length. The relation of these diameters is expressed by 

 the formula : 



Greatest breadth ^^^ou^r nf the iliac crests = Pelvic b"^'^^ index 



The average index for white races is 73. 



Pelvic Cavity. The measurements usually taken are those of the superior aperture. In 

 man there is a proportionate increase in the transverse diameter as compared with lower forms : 



Antero-posterior diameter (conjugate) from mid-point of sacral promontory 

 to the posterior margin of pubic symphysis x 100 



.j . , , rp *-^T. - TT^ = Pelvic or brim index, 



Greatest transverse width between ilio-pectineal lines 



Turner has classified the indices into three groups : 



Dolichopellic, index above 95 : Australians, Bushmen, Kaffirs. 

 Mesatipellic, index between 90-95 : Negroes, Tasmanians, New Caledonians. 

 Platypellic, index below 90 : Europeans and Mongolians generally. 



Vertebral Column. A characteristic feature of man's vertebral column is the pronounced 

 lumbar curve associated with the erect posture in the living. Apart from the consideration of 

 the interposition of the intervertebral fibre-cartilage between the segments, the bodies of the 

 lumbar vertebrae influence and react on the curve by exhibiting differences in their anterior and 

 posterior vertical diameters. Advantage has been taken of this to endeavour to reconstruct 

 the lumbar curve from the dried and macerated bones, but it must be borne in mind that habitual 

 posture or increased range of movements may yield results which are possibly misleading. 

 Thus there is reason for believing that the squatting position, when habitually adopted, may give 

 rise to a compression of the anterior parts of the bodies of the vertebrae which it might be 

 assumed was associated with an absence of or flattening of the lumbar curve, which in fact did 

 not exist during life. 



The quality of the curve is estimated from the macerated bones by an index which is com- 

 puted as follows : 



Sum of posterior vertical diameters of the bodies of five lumbar 



vertebra, x 100 _ . General lumbar index . 



Sum of anterior vertical diameters of the bodies of five lumbar 

 vertebrae 



