58 BIOLOGY AND SOCIAL PROBLEMS \ 



may be more generally effective than the 

 bull. 



Even from what is known at this early 

 stage in the study of hormones, it must be evi- 

 dent that they are most important substances 

 for the correlation of one part of the body 

 with another, and that in certain instances 

 they may rival though they never equal in 

 importance nervous methods of correlation. 

 Of course the whole plan of hormone interre- 

 lation is such that nothing can be expected 

 to spring from it, as the higher nervous func- 

 tions have grown from the simpler nervous 

 operations ; but, from the instances cited, it 

 must be clear that next to the nervous system 

 nothing will be found so potent for the con- 

 trol of animal activity as the hormones. 



In much of the preceding account, I have 

 dealt with the nervous system and the hor- 

 mones as though they were distinct and sep- 

 arate means of accomplishing very similar 

 ends. But as might be suspected by any one 

 who is conversant with the conditions in organ- 

 isms, both means are often most complexly 

 and intricately interwoven in the perform- 

 ance of a single act. This is well illustrated 

 in our respiration. Nothing seems simpler or 



