W. Koch and M. L. Koch 



425 



he is observing. As an example of this, there was studied 

 the ratio between neutral sulphur and protein sulphur, a ratio 

 which correlates closely with the decrease in metabolic activity 

 associated with the growth of the nervous system from birth to 

 maturity. 



The general plan of the chemical technique has been first to 

 block out the material into larger groups of substances and then 

 carry the procedure of separation into greater detail. The neces- 

 sity of working with data which represent something definite from 

 the point of view of the chemist, has also been kept in mind. 



The following outline illustrates the extent to which the chemi- 

 cal procedure has been carried up to the present. 



Outline illustrating the separation of constituents ~by the method employed, z classified 

 according to their state of aggregation. 



For an explanation of the chemical procedure followed for this 

 separation the following outline has been inserted. 



2 The method employed for this separation is described in an earlier 

 paper by W. Koch and coworkers: Journ. of the Amer. Chem. Soc., xxxi, 

 pp. 1342-1361, 1909. 



