64 FREDERICK S. HAM Ml TT. 



and millimeters per day) is greater in the former than in the 

 latter. 



Chart i depicts the values of the growth capacity (grams per 

 100 grams and millimeters per 100 millimeters per day) of the 

 bones and body weight and length at the stated ages. 



It shows that the growth capacity of the femur in weight and 

 length is generally greater than that of the humerus in both 

 sexes up to 65 days of age, and that thereafter the differences 

 are inconsiderable. As a result of this superiority the femur 

 becomes increasingly larger and heavier than the humerus up to 

 the age of 65 days, at which time systemic divagation is brought 

 practically to an end by the approximation to a common level 

 of the growth capacities of the two bones. At 65 days of age, 

 then, the systemic difference has reached the level characteristic 

 of the adult animal. The cessation of deviation at this time 

 indicates that the period between 23 and 65 days of age is the 

 period of systemic development of these bones just as it is the 

 period of their differential chemical development, and that the 

 culmination of puberty at 65 days acts as an equilibrating agent 

 with the one as with the other. 



In both sexes the growth capacity of the humerus in length is 

 quantitatively more nearly like that of the femur than is the 

 growth capacity in weight. As a result the increase in difference 

 in length between the two bones is less in degree than the in- 

 crease in weight difference. Hence the systemic difference in 

 serially homologous bones in the adult as in the immature 

 animal is less a difference in length than a difference in weight. 



The ratio of the gnyvvth capacity of the humerus to that of the 

 femur in both weight and length is generally of the same order of 

 magnitude in both sexes at all ages. But the chart shows that 

 there are sex differences in the course of the changes in growth 

 capacity with age during the period of differential development. 

 However, the course tends to be systemically characteristic even 

 though sex-specific in type. From this it can be concluded that 

 these systemic relations are practically sex-indifferent. They are 

 however, probably species specific. 



It is clear from the chart that there occurs a decrease in growth 

 capacity in w r eight and length of bones of both sexes on age. 



