DYNAMICS OF HISTOGENESIS 109 



3. The law of density of a growing tissue: The density of a 

 growing tissue is directly proportional to the resistances (pressure) 

 encountered during growth. 



4. The law of relative volume of a growing tissue : The relative 

 volume of a growing tissue is inversely as the resistances (pressure) 

 which it bears. 



5. Cartilage and bone do not self-differentiate, but they are 

 the cellular reactions to the varying mechanical resistances 

 (pressure) encountered by groups of cells in a field of differential 

 growth. 



6. The evidence supports the conclusion that resistance to 

 growth is active and formative during development, and that 

 the processes of histogenesis and morphogenesis of the skeleton 

 and muscles are as much dependent upon the mechanical factors 

 extrinsic to the region of the specific developing structure as 

 upon the intrinsic faculty of the modifying tissue to grow. The 

 modifying growing cells receive and respond to the mechanical 

 stimulus. The stimulus, however, is a function of position. 



LITEIL\TURE CITED 



Bardeen, Charles R. 1910 Keibel and Mall, Human Embn-ologv, vol. 1, p. 



320. 

 Carey, E. J. 1919-20 J. Gen. Physbl., (a) vol. 2, p. 357; (b) vol. 3, p. 61; (3) 



Anat. Rec, vol. 19, p. 199. 

 ScHULix, K. 1873 Arch. f. Anat. u. Physiol, Anat. Abth., S. 240. 

 Thoma, R. 1907 Virchow's Archiv, Bd. 188, S. 248. 



