2X1 



HENRY H. DONALDSON 



If the weight of a running millimeter as thus obtained, and 

 shown in charts 20 and 21, is accepted as the basis for compari- 

 son, it becomes easy by the use of this datum to follow the 

 changes in the dimensions of the cylinders which by assumption 

 represent the bones as they increase in size. 



Chart 20 Weight in milligrams of one running millimeter of fresh fore-limb 

 hones, on body weight (albino rat). No table. 

 • Humerus, x Ulna plus radius. 



Chart 21 Weight in milligrams of one running millimeter of fresh hind-limb 

 bones, on body weight (albino rat). No table. 

 • Femur, x Tibia plus fibula. 



It will be sufficient for the present purpose to use the data 

 for four body weights only, namely, at 5 grams, or birth; 20 

 grams, weaning time; 100 grams, or puberty, and 485 grams, or 

 maturity. 



