88 C. A. L. Bassett: Electro-mechanical Factors Regulating Bone Architecture 



vessels and, quite possibly, through the ballistics of cardia action. Gravity causes 

 not only direct distortion of the skeleton, but is major impetus for the muscle 

 tone which stabilizes the body against its effect. Trough aponeurotic origins and 

 insertions, this muscle tone intermittently deforms the underlying bone. When 

 voluntary muscle action is superimposed, additional mechanical stress is developed. 

 If In the course of the voluntary action, the skeleton makes contact with its environ- 

 ment, the shock wave from the impact may be transmitted throughout the skeletal 

 system. Pity the skeleton and kidneys of the poor astronaut who is subjected to 

 prolonged periods of weightlessness! He will lose the major portion of the last three 

 mechanical stimuli to bone and must, therefore, become osteoporotic at a more 

 rapid rate than those subjected only to bed rest. A better understanding of these 

 electro-mechanical factors may lead, in time, to improved methods for combating a 

 loss of bone mass, whether generalized as the result of inactivity, weightlessness, or 

 metabolic aberration, or whether localized as the result of rigid, internal fixation or 

 loss of function. 



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