» on the Conformation of Bones 381 



antero-posterior diameter of the condyles, so remarkable a feature 

 of running and jumping types, especially in certain extinct artio- 

 dactyla (see Fig, 3), must be a part of the same evolutionary 

 response to requirements. The internal structure of the deep con- 

 dyles illustrates their true nature. The data of Pearson and Lee* 

 provide an excellent illustration of this effect in the lower Primates, 

 though not so interpreted by them. Tarsius, Indris, and Nycti- 

 pithecus, all jumpers, contrast strongly with Apes, Loris, Mycetes 

 and othersf. Man again shows the deeper and narrower condyles 

 of active hind- limbs; how precarious must be an argument as to 

 his ancestry from a study of indices based on these measurements. 



Ficf. 3. Lower end of femur of Anthracotherium, showing deep condyles of a cur- 

 sorial type. From a specimen in the possession of Mr Forster Cooper, repro- 

 duced with his kind permission. 



without further knowledge of the knee-joint movements in various 

 animals. 



The importance of the shaft of a long bone as a surface for mus: 

 cular attachment is suggested by an examination of animals in which 

 transmitted propulsive forces are not great. They exhibit flattening 

 of the shaft, the width far exceeding the sagittal diameter; this is 

 conspicuous in the sloth. The great relative width is necessary for 

 provision of muscular attachments; there can hardly be lateral 

 strain sufficient to justify such width. The slow loris and apes are 

 broad in the shaft (Pearson and Lee). And when width of shaft is 



* Pearson and Lee, 'Long Bones of the English Skeleton.' Drapers' Company 

 Memoirs {Biometric Series), x and xi, pp. 329, 337, 412. . . 



t The length of the femur is a poor standard for comparison because of its great 

 variability with function. 



VOL. XX. PART III. ^^ 



