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HELEN DEAN KING AND HENRY H. DONALDSON 



tions at G 5 , G 6 , and G 7 are clearly marked. At the same 

 time, the deviations in the percentage of water follow the 

 deviations in weight. On considering these changes together, 

 it appears that when the femur is less in weight the medul- 

 lary cavity also becomes less, and as this cavity carries water- 

 bearing materials the percentage of water is thereby dimin- 

 ished. The deviation in the percentage of water in this case 



TABLE 25 



Giving the percentage deviations for the weight, length, and percentage of water 

 in the femur of the captive Grays 



is, therefore, not to be referred to the osseous tissue in the 

 strict sense, but to the entire bone as an organ. 



There is one feature in these graphs that calls for comment, 

 namely, the frequency of low values at G 5 . In series 1 the 

 first low value marking a sag in the graph usually comes at 

 G 6 . We infer from this relation that the unfavorable con- 

 ditions which are assumed to produce these retardations are 

 effective in modifying the skeleton in animals that are older 

 than those in which the several organs are affected (chart 1). 



