1542 GROWTH. [BOOK iv. 



the kidneys, these like the skin increasing in weight twelve times 

 only between birth and full growth, whereas the whole body 

 increases twenty times. The heart and the liver according to the 

 newer observations behave very similarly, and even according to 

 the older observations lag considerably behind the whole frame, 

 whereas the lungs and the alimentary canal almost exactly keep 

 pace with it, and the skeletal framework, in spite of its being 

 specifically lighter in its earlier cartilaginous condition, maintains 

 throughout life very nearly the same relative weight. The muscles 

 on the contrary grow more than twice as fast as the whole body ; 

 the great increase in these covers the relative decrease of the 

 other parts, and it is largely by the laying on of flesh and fat 

 that the babe gains the bulk of the man. 



973. We usually measure growth by taking account of two 

 sets of changes, changes of stature and changes of weight ; and we 

 may study both these changes in more than one way. 



If we measure the height at intervals we may plot out the 

 curve of growth of stature ; and when we do this we find that the 

 curve rises rapidly at first but afterwards more slowly, shewing 

 that the increment is decreasing, and at about the twenty-fifth 

 year ceases to rise at all. From thence to about fifty years of age 

 the height remains stationary, after which there may be a decrease, 

 especially in extreme old age. The curve moreover is not regular, 

 but indicates by its changes that the increment of height in a 

 given time is now smaller, now greater. 



The curve of weight is, on the whole, at first very similar to 

 that of height, rising in a somewhat similar way and shewing similar 

 irregularities ; but instead of ceasing to rise at about the twenty- 

 fifth year it continues to rise, though marked with many irregulari- 

 ties, and may continue to do so until about the fortieth year. After 

 the sixtieth year a decline of variable extent is generally witnessed. 

 It should be noted that in the first few days of life, so far from 

 there being an increase, there is an actual decrease of weight, so 

 that, even on the seventh day the weight still continues to be less 

 than at birth ; and a similar post-natal loss of weight is observed 

 in animals. If we take the curve of growth from the impregnation 

 of the ovum onwards this post-natal loss of weight will appear as 

 an abrupt change in the curve due to the so to speak violent act 

 of birth. It should be added that the curves both of height and 

 weight exhibit differences dependent on sex, circumstances, race, 

 climate and the like. 



We may also study the progress of growth by measuring 

 the increment of growth in a given time, in a year for instance, 

 and plotting out the curve of the yearly increment. When we 

 do this we obtain very instructive results. We find that the 

 yearly increment decreases very rapidly during the first two or 

 three years, then remains nearly stationary or even rises, and 

 at about the seventh or eighth year undergoes a marked fall. 



