320 



GROWTH OF CHEMICAL CONSTITUENTS 



The sex differences in absolute amounts of ash, and of calcium, 

 magnesium, and phosphorus of the ash at both ages are too small to be 

 individually valid, yet the consistency of the direction of deviation 

 shows that the bones of the females at 100 days of age have absolutely 

 greater amounts of ash, calcium, magnesium, and phosphorus than do 

 those of the males, and that at 150 days the conditions are reversed. 

 The correctness of this supposition is supported by the fact that the rate 

 of growth of the humerus and femur in the male rats during the period 

 of observation is greater than that of the females in weight, length, 

 water, organic matter, ash, calcium, magnesium, and phosphorus. 



There is apparently a slight difference between the results 

 given in table 176 and those obtained when the diaphysis alone 

 is analysed (Toverud, '23) table 177 (1). This latter table con- 

 tains also the corresponding data (2) for the molar teeth and (3) 

 for the incisors. 



TABLE 177 

 Inorganic constituents of the femur and teeth {Toverud, '23) 



(1) Analysis of bones (Diaphysis of femur). 



Average from three mature rats — two males, one female — fed on normal 

 mixed diet. 



(2) Analysis of molar teeth. 



(3) Analysis of incisor teeth. 



On a calcium deficient diet a decrease in total ash and calcium 

 oxide occurs in all the tests made, Toverud ('23). The occurrence 

 of this change in the permanent molar teeth is especially worthy of 

 note. 



3. In the nervous system. With the purpose of following the 

 changes in the chemical constituents of the brain with advancing 

 age, Koch, W. and M. L. ('13 a) have made a series of observa- 

 tions and to these have been added also observations on one spinal 

 cord at 120 days. The results are given in tables 178 and 179. 



In chart 57 are given the graphs for the absolute weights of 

 the more important chemical constituents of the brain plotted on 

 age (see table 179). 



