108 EBEN J. CAREY 



C. CONCLUSIONS 



1. The apparently continuous blastemal skeleton is in reality 

 segmental and composed of centers of accelerated growth opposed 

 in action. 



2. By the continued opposition to growth between the con- 

 tiguous centers of the segmental blastemal skeleton, mechanical 

 compression occurs, revealing the location of the future joint 

 cavities. 



3. The contour of the opposed surfaces constituting a joint 

 is dependent on the intensity of the force of growth per square 

 millimeter of cross-section of growing segments opposed in action, 

 together with the force of muscular pull. That segment will 

 possess the ball of a ball-and-socket joint, which possesses the 

 greater force of interstitial growth longitudinally per square 

 millimeter of cross-section. 



4. Joints, therefore, are not the cause of skeletal segmentation; 

 they themselves are the mechanical resultants of compressive 

 and shearing stresses of prior centers of accelerated growth 

 opposing each other in action in the segmental blastemal skeleton. 



5. Law of joint formation: The contour of the opposed surfaces 

 forming a joint is dependent upon the intensity of the force of inter- 

 stitial growth per square mUlimeter of cross-section of the skeletal 

 segments forming the joint and upon the force of muscular pull. 



7. CONCLUSIONS 



1. Skeletal condensation, varj^ing through the different degrees 

 of density, beginnmg with the blastemal period, progressing 

 through the cartilaginous, and terminating in the osseous period, 

 is a direct resultant of the varying intensity of the resistances 

 (pressure) encountered during the period of growth. 



2. The resistances to femoral growth are as follows: 1) Weight 

 of the hind limb; 2) reactive force of elasticity of traction of the 

 foiming muscles ; 3) active muscular pull; 4) opposition to inter- 

 stitial femoral growth at the ends by the acetabulum proximally 

 and the tibia distally. The evidence presented in this paper 

 warrants the formulation of the following laws: 



