2 PHYSICAL EXPRESSION. 



impressionability of the nerve-mechanism in child- 

 hood, and the immense importance of such impres- 

 sions on the future moral and intellectual condition 

 of the child. 



In every scientific inquiry, whatever be the 

 ultimate object in view, it is necessary to use 

 the utmost accuracy as to method of procedure. 

 The present work contains an analysis of some of the 

 usual means of investigating the nerve-system, with 

 a view to the establishment of an experimental 

 method of inquiry as to the forces leading to its 

 growth and development (see chap, xix.), This 

 is a somewhat bold and ambitious project, and no 

 one can be more conscious than the author of the 

 difficulties that lie in the way. One special object 

 in view is to show how much accuracy and clear- 

 ness of insight may be obtained in biological work 

 by dealing as much as possible with objective signs 

 and physical forces only, always adhering to the 

 postulate that every objective phenomenon must be 

 the outcome of physical action. 



My early studies were on the size, shape, and 

 proportions of the head, as indicative of the brain 

 within. Such observations led to but poor results ; 

 still, they were useful. The results of these obser- 

 vations are embodied in the account given of co- 

 incident development (see chap, xvi.).* I next set 

 about considering how our knowledge of brain 

 functions had been obtained, and analyzed the 

 methods employed in such physiological work ; and 



* Mr. Charles Roberta's excellent manual on anthropometry gives 

 much valuable information on this subject. 



