1 8 AGE, GROWTH, AND DEATH 



begins, and then continues almost steadily to the 

 very end of life. 1 



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 mo- 

 ments 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 given, you must 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, particu- 

 larly from that product which we know as carbon 

 dioxide. The result of the combustion going on in 

 the body (which in one of its end terms appears to us 

 as carbon dioxide expelled from the lungs) is to pro- 

 duce heat, to develop the necessary warmth for the 

 maintenance of the proper temperature of the body. 

 Now in the very young the bulk of the body is not 

 great, but the loss of heat is very great, and this per- 

 haps can be most readily explained to you if you 

 imagine that you hold in one hand a very small 



1 For further details the reader is referred to the invaluable work by 

 Professor H. H. Donaldson of the Wistar Institute, The Growth of the 

 Brain. A Study of the Nervous System in Relation to Education, I2mo, 

 London, 1895 (Walter Scott). 



