238 HENRY H. DONALDSON 



MATERIAL 



From albino rats between birth and old age, 106 skeletons 

 were prepared by Miss Conrow, the work extending from 1913 

 to 1917. Of these skeletons, 85 were from inbred rats taken 

 from Dr. King's inbred series and the remainder were from stock 

 Albinos, all the animals having been reared in the colony at 

 The Wistar Institute under uniform food conditions. Each 

 skeleton contains 283 bones, including and counting the teeth. 

 In the preparations here examined there were, however, only 

 230 bones, prepared separately, and these in turn were weighed 

 in twenty-eight lots, in the case of each rat. 



The details concerning the composition of the skeleton and 

 the number of bones prepared for weighing are given in Appen- 

 dix 1 . All these skeletons have been stored, after being dried at 

 96°C. for six days. 



In addition to this series of entire skeletons the long bones of 

 the limbs were similarly prepared from 54 young albino rats 

 (males 32, females 22; body weight 5 to 86 grains ; age, birth to 

 64 days) and the data on these bones were combined in tables 

 8, 9, 11 to 14, 20, and 23 with those from the series of complete 

 skeletons, according to body weight or to age. 



With this material we purpose to show in the first instance 

 how the entire skeleton increases in weight in relation to the 

 total body weight and to age. Then, the growth of its several 

 divisions and parts, 1) in relation to that of the entire skeleton, 

 and, 2) in relation to the weight of the entire body; also the 

 relative growth of the three divisions of the fore limbs and of 

 the hind limbs, respectively. At the same time the change in 

 the percentage of water with growth has been followed in both 

 the entire skeleton and its various parts, and finally, the increase 

 in the length of the long bones both of the fore limbs and of the 

 hind limbs has been determined, in relation both to the body 

 weight, to the body length, and to one another. 



We hoped to discover that in some parts of the skeleton the 

 length or weight of the bones was so well correlated with the 

 data for the entire skeleton that it would be possible, in any 

 instance, to compute the body length or the weight of the entire 



