Porter — The Growth of St. Louis Children. 343 
weight, girth of chest, strength of squeeze and other physical 
dimensions up to the mean development which corresponds to 
the height of the child. Experience has abundantly shown 
that the relation of weight to height is of great importance to 
health, life insurance companies declining to receive applicants 
whose weight falls much below the standard weight of their 
height. For these reasons, height should be preferred as the 
basis of the system. 
The question whether any given deviation is normal or 
abnormal is answered by this system in two ways: in respect 
of height, by the degree of deviation from the mean or norm 
of the whole number of observations; in respect of other 
dimensions, by the degree of deviation of the weight, girth of 
chest, etc., from the mean weight or girth of chest corre- 
sponding to the height of the individual under examination, 
this normal weight, etc., being determined with sufficient 
exactness by taking the means and probable deviations of the 
group in which the height falls. It is evident that all cases 
included within M-+-d must be termed normal, for the chances 
are even that any individual measurement in a series will fall 
within M-d and are against its exceeding these limits, being 
4.64 against 1 that it will fall at M+2d. 
Strictly speaking, all abnormal deviations in any dimension 
are probably unhealthful, yet an important difference exists 
in this respect between abnormal deviations in height and 
abnormal deviations in weight, girth of chest, etc., as related 
to height. It cannot be doubted that abnormal height is 
probably (using the word in its technical sense) a disadvan- 
tage. The potential energy of the body is converted into 
mechanical labor and heat, by far the greater expenditure 
taking the latter form. In the adult, the total expenditure 
in the form of heat is about 2,700 calories in 24 hours 
(Helmholtz), of which 80.1 per cent escape in radiation, con- 
duction and evaporation from the skin. Thus the superficies 
of the body plays a great part in the dissipation of energy. 
The superficies is greater, usually, in tall children than in 
short, a difference of special importance in the young, in 
whom metabolism is much more active than in the adult. 
More heat is therefore lost by the abnormally tall than by 
