KINETOGENESIS. 283 



b. Normal Articulations. 



The origin of condyles and their corresponding 

 cotyli has been made the subject of investigation by 

 several German anatomists. L. Fick^ expressed the 

 opinion that the concavo-convex surfaces were pro- 

 duced by a wearing away of the surface which became 

 concave, by the free action on it of the surface which 

 became convex, the former being fixed, and the latter 

 free. He found the conditions of muscular insertions 

 to correspond with the conditions of fixity and free- 

 dom required ; for the insertions are always nearer to 

 the concave surface than to the convex surface. He 

 constructed plaster models of joints, and by moving 

 one on the other obtained a convex surface on the 

 moving, and a concave surface on the fixed extremi- 

 ties. These observations were confirmed by Henke,'-* 

 but he very properly does not regard the result as due 

 to wearing, but to the stimulation of metabolic action 

 in the required directions. R. Fick^ has confirmed 

 these positions in an extended memoir, and recently 

 Dr. E. Tornier has devoted a still more thorough re- 

 search to the same subject.^ R. Fick applied his ob- 

 servations to the question of the phylogeny of the ar- 

 ticulations, but did not see in it proof of the operation 

 of mechanical causes, but ascribed it to "inheritance 

 and natural selection " in accordance with the mean- 

 ingless formula usual at the time he wrote. W. Roux,' 

 however, in reviewing Fick's article saw in the obser- 



1 Ueber die Ursachen dcr Knochen/ormen , Experimental - Untersuchung, 

 1859, Gottingen, G. Wiegand. 



^Anatomic iind !\Iechanik dcr Gelenke, Leipsic, 1863, p. 57. 

 Z Archivfiir Anatomie und Physiologic, 1890, p. 391. 

 i Archiv/iir Entwickelungsmechanik, I., 1894, p. 157. 

 6 Biologisches Centralhlaii, 1891, p. 188. 



