GROWTH OF THE SKELETON 



267 



more constant than the percentage after room drying, and in one 

 sense this is true. 



As chart 13 shows, there is a rapid fall of about forty points 

 in the percentage of water up to puberty, or to about 100 days of 

 age, and after that a loss of about five points during the remainder 

 of life. 



As indicated by the discussion on the effects of the macerating 

 fluid (Appendix 2) , the data for the percentage of water are about 

 0.6 per cent low at birth, and this deficiency increases about 0.04 

 per cent for each 5 grams increase in body weight, up to 150 



Chart 13 Percentage of water in the entire skeleton — oven dried — on age 

 and on body weight (albino rat). Table 15. 

 • Age. x Body weight. 



grams, after which the deficiency remains constant. The relative 

 values in the different parts of the skeleton are, however, not 

 affected by the maceration. 



During early life calcification of bone is largely a function of 

 age, and it seemed desirable, therefore, to compare the course of 

 the percentage of water in the entire skeleton when the values were 

 entered according to the observed ages as in the left-hand por- 

 tion of table 15, under A, and when entered according to body 

 weights, as in the right-hand portion of table 15, under B. The 

 corresponding graphs for the entire skeleton are given in chart 13. 



As the records show, after puberty there is no marked differ- 

 ence brought out by the two methods of presentation, which 

 means merely that there is little further change in the percentage 



