AGE, GROWTH AND DEATH 487 



a curious change going on, a change of which old age presents to us 

 the culminating record. In order to study the weight of the brain, 

 it is necessary to compare people of the same size, for the size and 

 weight of the brain depend somewhat upon the size of the individual. 

 Now it has been discovered by careful examination of persons of 

 similar size that the brain begins relatively early to diminish its 

 weight. Thus in persons of a height of 175 centimeters, and over, 

 of the male sex, it is found that in a period of from twenty to forty 

 years the brain weight is 1,409 grams. But from forty-one to seventy 

 years it has sunk to 1,363, and in persons of from seventy-one to 

 ninety it has shrunk to 1,330. Women of corresponding size are not 

 easily found, and a more average height for women is 165 centimeters; 

 a woman of such a height is likely to have — among the white races, 

 be it always understood — a weight of brain of 1,265 grams, at forty 

 to seventy years a brain of 1,200, and at seventy-one to ninety years 

 a brain of only 1,166 grams. 4 I give these figures because they show 

 that there is no guessing, but a definite, positive knowledge, proving 

 that soon after the maturity of life in the individual is reached, the 

 shrinkage of the brain begins, and then continues almost steadily to 

 the very end of life. 



It is not only the anatomist, but it is perhaps almost equally the 

 physiologist who gives us insight into the changes, which go on in 

 the old. I spoke a few moments ago of the pulse rate, and of the 

 change which that offers. At first sight it seems as if a greater pulse 

 rate indicated an improvement, but if you recall the explanation which 

 I have given you, you will acknowledge that this is by no means an 

 acceptable interpretation, but that on the contrary the change is a 

 clear mark of enfeeblement. In the respiration, also, we observe a 

 like change. Here the comparison is not quite so easy as we should 

 at first imagine, because there is a relation between the size of the 

 individual and the respiration. The respiration, as you all know, frees 

 the body from the products of combustion, particularly from that 

 product which we know as carbon dioxide. The result of the com- 

 bustion going on in the body (which in its end term appears to us as 

 carbon dioxide expelled from the lungs) is to produce heat, to de- 

 velop the necessary warmth for the maintenance of the proper tem- 



i 



Ernst Handmann has recently published statistics on the growth of brain, 

 based on measurements at the Leipzig Pathological Institute. See Archiv f. 

 Anat. u. EntwicJcelungsges., 1906. p. 1. The following summarizes his results: 



Brain Weight in Grams 

 Age Male Female 



4-6 1215 1194 



7-14 1376 1229 



15-49 1372 1249 



50-84 (89) 1332 1196 



