2XN 



IIKNKY II. DONALDSON 



been divided by the length of the humerus, and the length of the 

 tibia by that of the femur. The ratios are given as percentages 

 also in table 27 and the corresponding smoothed graphs are shown 

 in chart 22. 



Finally, the homologous bones in the two limbs have been 

 compared as to their growth in length; radius or ulna divided by 

 length of tibia, and the length of humerus by that of the femur; 

 (table 28, chart 23). 



40 



20 



50 



100 



Growth of Skeleton— Albino Rat 

 Fresh 



Ratios of Bone length 



150 



200 



250 



300 



350 



BODY WEICHT IN CRAMS f 



I M I I II I I I I II 



400 



460 



Chart 22 Ratios of fresh bone lengths, on body weight (albino rat). 

 Table 27. 



o 



Radius + Humerus 



Tibia + Femur 



Radius Ulna 







Humerus 



X 



n 



Humerus 



Ulna + Humerus 

 Tibia + Femur 



Tibia 

 A 



Femur 



There are two large relations which stand out clearly in this 

 comparison. During early life the length of the bones of the 

 hind limb increases more rapidly than that of the bones of the 

 fore limb (table 27, chart 22), so the percentage value for the 

 fore-limb bones diminishes from birth, at first rapidly, up to 

 about 50 grams of body weight (or thirty-five to forty-five days 

 of age), but after that period it remains practically constant. 



