GROWTH OF THE SKELETON 239 



skeleton from the value of a portion of it. Tables 9, 23, and 24 

 which follow show that this result has been attained. 



Many series of computations and tables have been made and 

 are complete in manuscript form, but we shall use only a portion 

 of them for the present paper. Copies of all of the tables have 

 been filed, however, in the archives of The Wistar Institute and 

 are at the service of other investigators. 



TECHNIQUE OF PREPARATION 



For the details of the technique the reader is referred to Appen- 

 dix 2. In general the procedure was as follows: The recently 

 dissected parts of the skeletons were macerated by immersing 

 them in 50 to 200 cc. of a hot 2 per cent solution of commercial 

 'Gold Dust.' This treatment left the bones from the older rats 

 nearly unmodified as to their weight and water content. 



The precise effect on the bones of rats of different body weights 

 ( = ages) are given in detail in Appendix 2. 



The macerated bones were weighed in closed bottles, first 

 fresh (i.e., immediately after maceration), then after room drying 

 for thirty days in the open air, and finally after six days in the 

 oven at 96°C. Where lengths were measured, these also were 

 taken in the three conditions of moisture. All the determina- 

 tions and computations were made separately for each rat, but 

 the results were later combined in body-weight groups. Between 

 4.3 grams and 15 grams of body weight, the groups were made at 

 5-gram intervals, and after that at intervals of 10 grams. This 

 arrangement yielded forty-two body-weight groups ranging from 

 birth to 513 days of age, and from 4.3 to 485 grams in body 

 weight. 



The foregoing statements apply to all the records except 

 those for the lengths of the long bones of the limbs. In these 

 cases the data from the additional fifty-four rats were combined 

 with those from the main skeleton series, with the result that in 

 the records for bone length there were formed forty-seven, in- 

 stead of forty-two, body-weight groups. 



The tables, charts, and discussion which follow are based on 

 these group values, but are presented in a modified form, as will 



