PHASES IN THE LIFE OF THE INDIVIDUAL 719 





It has been shown also that the brain decreases in size in old age. 

 The shrinkage begins soon after maturity, and then continues almost 

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

 following statistical results, which are based on measurements 

 carried out at the Pathological Institute at Leipzig :— 



Weicjlit of Brain. 

 Ar,e. 



4-6 . . , 



7-14 

 15-49 

 •'■)0-84 



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. Those changes are 

 associated on the psycliical side 

 with a gradual mental failure — 

 loss of memory, decrease in the 

 power of original thought aud in 

 the assimilation of new ideas, and 

 general decline of mental activity. 

 Moreover, the reaction time is 

 lengthened, the sense ijrgans lose 

 their delicacy, and in the eye 

 the power of acconnnodation is 

 largely lost. 



The minute cellular changes 

 in the tissues are no less pro- 

 nounced. These also are in tlie 

 direction of atrophy. There is a 

 general shrinkage in the proto- 

 plasm of the cells, liut 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 ^ has made a comparison of tlie changes in the 

 cells of the first cervical ganglion with the followino- result : — 



Fit: 



186. — Group of iierve-cells from 

 the Hrst ceivical ganglion of a 

 child at birth. (After Hodge, 

 from Minot's Aye, (Jruirth, and 

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

 .John Murray.) 



At birth 

 At 92 years 



Vuluine of Slide 



100 pel' cent. 

 64-2 „ 



Xueleoli ohsermhle 

 in Siielenx. 



In 53 per cent. 



' Minot, loc. eit. 



^ Handmann, " Uber das Hirngewicht des Menschen," Areh. f. Anat. ii. Pliij.t., 

 Anat. Abth., 1906. 



^ Hodge, "Die Nervenzelle bei der Geburt und beim Tode an Altersehwiiche," 

 Anat. An^., vol. ix., 1894. 



