724 



AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



B. GROWTH-CHANGES. 



The characters of the brain and cord thus far described have been those 

 found for the most part in the adult. Between birth and the natural end of 

 life, however, great changes take place, and, as it is necessary to consider the 

 functions of the central system at all times in its history, the importance of 

 knowing the direction in which the growth-changes are probably occurring is 

 obvious. 



Growth of Brain. The weight of the brain from birth to the twenty-fifth 

 year is given below (Vierordt l ). 



Increase in Brain-weight with Age Emephalon Weighed Entire with Pia 



(compiled by H. Vierordt}. 



Total number of cases, 415. 



Total number of cases, 424. 



From the same figures the first part of the accompanying curve (Fig. 204) 

 has been formed. 



The curve beyond the twenty-fifth year is continued on the basis of the 

 observations by Bischoff, 2 and for comparison the curve representing the 

 encephalic weights of a series of eminent men, forty-five in number, is drawn 

 in a dotted line, the averages for decennial periods being alone plotted. 



These records exhibit the fact that at birth the weight of the brain is about 

 one-third of that which it will attain at maturity. The increase is very rapid 

 during the first year, and vigorous for the first seven or eight years, after which 

 it becomes comparatively slow. The maximum weight is indicated in the 



1 Archivfiir Anatomic und Physiologic, 1890. 2 Hirngewicht des Menschen, Bonn, 1880. 



