PHASES IN THE LIFE OF THE INDIVIDUAL 719 



It has been shown also that the brain decreases in si/e in old age. 

 The shrinkage begins soon after maturity, and then continues almost 

 steadily to the very end of life. 1 Handmann- has published the 

 following statistical results, which are based on measurements 

 carried out at the Pathological Institute at Leipzig : 



\Vi-nflit of Iti-nin. 



Age. M'il>'. Female. 



4-6 - - 121") gram>. 1194 grams. 



7-14 - 1376 1229 



l.')-4!) 1372 1249 



50-84 1332 ., 1196 



The decrease in brain weight is accompanied by a diminution in 

 the thickness of the cortex and in the number of tangential fibres 

 present in it. These changes are 

 associated on the psychical side 

 with a gradual mental failure 

 loss of memory, decrease in the 

 power of original thought and in 

 the assimilation of new ideas, and 

 general decline of mental activity. 

 Moreover, the reaction time is 

 lengthened, the sense organs lose 

 their delicacy, and in the eye 

 the power of accommodation is 

 largely lost. 



The minute cellular changes 

 in the tissues are no less pro- 

 nounced. These also are in the 

 direction of atrophy. There is a 



FIG. 186. Group of nerve-cells from 

 the first cervical ganglion of a 

 child at birth. (After Hodge, 



from Mind's .!//<, Hi-<rtlt, "/></ 

 Death, (1. S. Putnam & Sons, and 

 John Murray.) 



general shrinkage in the proto- 

 plasm of the cells, but especially 

 in the nuclei, so that the relative 

 amount of cytoplasmic to nuclear 

 substance becomes increased in 

 old age. The nucleoli also tend to 



disappear. Hodge 3 has made a comparison of the changes in the 

 cells of the first cervical ganglion with the following result : 



At birth 

 At 92 years 



100 per cent. 



64-1' 



in ,V"''/''".v. 



In "''} per cent. 

 11 5 



1 Minot, loc. 



2 Handmann, "Uber das Hirngewicht des Menschen," .!/'/'. /'. A fit. ". /'//.<., 

 Anat. Abth., 1906. 



3 Hodge, "Die Nervenzelle bei der ( ;>l>urt mid beim Tode an Alterschwiuhe," 

 Anat. .1/c., vol. ix., 1894. 



