494 PATON— CORRELATION OF STRUCTURE [April i8. 



The special instances which we have cited are a few taken from a 

 long list of experiments and the results as given may be considered 

 to be characteristic of all the cases observed. It is quite unneces- 

 sary to repeat in detail the experiments in which strychnia sulphate 

 was used as the results for solutions varying in strength from 

 1 : 5,000 to 1 : 10,000 practically corresponded with the records for 

 thyroid extract. 



An extremely interesting field of work lies in the direction of 

 determining with more exactitude than has yet been done the varying 

 degrees of responsiveness of the organism to these toxic agents at 

 different periods in the early development of the embryo. An ex- 

 ceedingly complicated problem but one of great importance would be 

 the determination, if possible, of the change in the symptoms as the 

 embryo develops and the probable progressive increase in the perme- 

 ability of the cells for the different solutions. This question must 

 be solved before we can appreciate the character of the changes in 

 the reactions taking place within the organism when the control of 

 functions is taken over by the nervous system. 



Princeton University, 

 April 18, 1913. 



