GROWTH OF THE SKELETON 



297 



is, therefore, a period of relatively rapid increase in the weight 

 of the skeleton shortly after birth which is shown in both studies. 

 At maturity the fresh skeleton as prepared by them represented 

 about 11 per cent of the body weight, while as prepared by us it 

 represents about 5 per cent. 



That this difference is due to the method of preparation was 

 shown by the fact that when Professor Jackson kindly dissected 

 for us in our laboratory a skeleton which was duly weighed and 

 then further prepared by the macerating process, which we 

 employed, and again weighed, the several values obtained in 

 this test stood in the relation which has just been given. 



In this connection we have also to consider the determinations 

 made by Lowrey ('13) of the dry substance in the ligamentous 

 skeleton of the albino rat. If the percentages of water are de- 

 rived from the percentages of the dry substance, it appears that 

 Lowrey' s determinations give a higher water content than that 

 found by us, especially in the later age groups. The difference is 

 not great, however, and seems easily referable to the greater 

 amount of soft tissue present after his method of preparation, 

 combined on the other hand with the slight reduction in the 

 water content caused by the maceration of our material. 



In a study of the weight of the room-dried cranium (Donald- 

 son, '12, table 4) determinations were made for five body-weight 

 groups of Albinos grown in The Wistar Institute colony. The 

 values there given are in close agreement with those presented 

 in our table 3. They are as follows (table 30) : 



We have, however, not made any measurements on the crania 

 of our series that might be compared with the observations of 



