6 PKKI-A( I-.. 



emphasise some more neglected points. Let me enume- 

 rate a few : the growth of the nervous system compared 

 with that of the body ; the interpretation of brain-weight 

 in terms of cell structure ; the early limitation of the 

 number of nerve cells ; the peculiar relation in this 

 system between increase in size and in organisation ; 

 the large though variable number of cells which have 

 but slight importance in the final structure ; the domi- 

 nance of nutritive conditions ; the wide diffusion of 

 nerve impulses ; the incompleteness of repose ; the 

 reflex nature of all responses ; the native character of 

 mental powers ; and the comparative insignificance of 

 formal education. 



To those who deal with the nervous system as it 

 grows, the facts within these covers will, I trust, be 

 useful ; the parent, the teacher, and the physician 

 represent three classes who seek for light upon such 

 matters, and it would be fortunate if, as a result of their 

 demands, there soon should be supplied an account of 

 growth far more extensive and more luminous than this. 



In putting together the materials employed, I have 

 sought the counsel and assistance of my friends who 

 took an interest in the work, and to them I would 

 express my gratitude, yet without transferring my 

 responsibilities. Save in a few cases, the illustrations 

 in this book have been copied from standard works, 

 and I am greatly indebted to both authors and pub- 

 lishers for the uniform courtesy with which permission 

 has been granted to have this done. To Messrs. 

 Macmillan & Co., publishers of Foster's Physiology ; 

 Longmans, Green & Co., publishers of Ouain's Anatomy ; 

 Ginn & Co., publishers of The Journal of Morphology ; 

 D. Appleton & Co., publishers of The Popular Scienct 

 Monthly > and to the proprietors of The Lancet, my 

 acknowledgments are especially due. 



CHICAGO, May, 1895. H. H. D. 



