I— PHYSIOLOGY 201 



The suggested explanation of the kink at 29 in. is the exercise taken by 

 the child when he or she begins at first to crawl and later to run about ; these 

 activities burn up fat and consequently the luxus consumption associated 

 with the fat storage and over-nutrition of babyhood disappears, which 

 means that the higher carbon dioxide production in proportion to body 

 weight becomes lessened. On this view the baby in early infancy leads 

 a vegetable existence, absorbing nutriment without much activity ; above 

 one year old he gradually becomes an energetic child. If this is true, 

 there should be a kink in the reverse direction when the logarithms of the 

 height and body weight are plotted against one another, because at this 

 point the baby would increase in height but not correspondingly in weight 

 as the nutrition became lower ; this was found to be the case and there 

 was a second kink at 41 1 in. (between 5 and 6 years), which also 

 coincided with and explained the change in the log. COj-log. weight 

 relation at this height. There are, thus, 3 nutritional periods in post- 

 natal life ; during the first the child puts on fat, and both the body weight 

 and the metabolism increase rapidly as the result and luxus consumption 

 becomes established. (There is also luxus consumption in the exogenous 

 obesity of adults) ; in the second period with the loss of fat the increase 

 in body weight is less, while the metabolism remains almost stationary ; 

 in the third period the increase in body weight and metabolism with 

 growth is again established, but in neither is the increase as rapid as in the 

 first period, since there is not the same amount of fat deposited. 



Emphasis has been laid on height rather than age or weight in deter- 

 mining the metabolism of an infant, and this suggests that the other 

 landmarks of development, such as the eruption of teeth, power to lift 

 the head, closure of the fontanelle, should also be related primarily to 

 height. 



Example (2 first cousins). 

 (i) First tooth at 27 weeks 22 lb. 27I in. 



(2) „ „ 37 .. i6| „ 28 „ 



Dr. H. St. J. Vertue, who is kindly making observations at the Salamon 

 Centre, Guy's Hospital, writes : ' Up to the present my figures (for 

 eruptions of first teeth) do show a wide disparity of age and weight 

 and not much disparity of length.' 



These three nutritional periods of childhood with their varying effect 

 on body weight suggest that the relation of body weight to age would not 

 be a satisfactory measure of growth, and this is borne out by the S-shaped 

 curve (unique for man) that is obtained when weight and age from birth 

 to puberty are plotted against one another. A much simpler curve is 

 obtained when height and age are related ; this is the ' cumulative growth 

 curve.' Above 6 years it is roughly linear till near puberty, when there 

 is an increase in growth, forming the so-called prepubertal rise. Such 

 curves (and they can be drawn back into prenatal life) are the best 

 measure of growth, and they demonstrate that on the average children 

 are taller than they were 56 years ago, and that children from better-class 



H 2 



