GROWTH OF SYSTEMS 



77 



obtained. The differences between the values for the moist 

 skeleton after maceration and those obtained after gross dissec- 

 tion may be designated as values for the 'periosteum, ligaments, 

 etc.' and are so entered in table 52. 



It is thus possible from these two tables to compare subse- 

 quent determinations of the skeleton after either dissection or 

 maceration. 



If rats normal in body weight for their age are compared, we 

 find that the cartilaginous skeleton at birth represents 52.5 per 



Chart 5 Giving for the sexes combined the percentage of the entire body 

 weight represented by each of the several systems. Plotted on age in days. 

 Table 50, Jackson and Lowrey ('12). 



cent of the weight of the ligamentous skeleton, while at one year 

 it represents 64.5 per cent. The ratio for the weight of the bony 

 skeleton rises therefore one point for each .23 grams increase in 

 body weight, or for each gram of increase in body weight the ratio 

 rises about 0.044 of a point. Within the age limits here given, 

 these factors may be used for transforming one set of values into 

 the other. 



