176 Trans. Acad. Sct. of St. Louis. 
It cannot be by chance that ages ten and twelve have yielded 
these results, so exactly fulfilling the expectations raised by 
the analysis of weights. What is true of these ages is un- 
_ doubtedly true of all ages in the period of development. 
There is no reason to apprehend that other dimensions, such 
as height sitting, span of arms, etc., are execptions to the 
law which has been shown to exist in respect of weight, height 
standing, girth of chest and width of head. 
We have thus far in this paper dealt with the dimensions of 
children of the same age. The relation between precocity and 
the rate of growth or yearly increase in size has not been 
considered, and to this most interesting subject we must now 
turn. 
The material for the comparison of the rate of growth of 
dull and precocious children is found in the weights of boys 
and girls distributed by school grades. The manner of treat- 
ing this material will be best understood by a statement of 
the method used in getting the weight of the mean dull 
and the mean precocious child at any age. Girls aged 13 
may serve as an example. Their distribution by school 
grades is as follows: 
School — No. of Observations. 
Ss SEN PES Re SR FT 6 
ss 6 nie GRE eek Pes OA ES ee Oe 41 
BEd hier eee sate ew RSE re os re SEO roe ees 129 
BV saci cies aon eee eae is Oude OIA Oe ete es 363 
MSS: SS. a ee A ee a ee one 331 
Di ee Pe ss 800 
oda RV ERE or oe See LE OS PS TS 121 
SE ee eS ee ee ee a eee ae ote ca le 37 
bea Henly. ssa ees wre heii A SR ES ee TE 6 
Rabelais ere Reis Se i ee 1,334 
The mean success in school life of girls at this age is in- 
dicated by the mean of these nine grades. Fifty per cent 
statement that the more successful children are taller and have — chests 
than the less successful, but finds a uniform rate of growth in these 
dimensions. 
My own results were reached before I knew of the work of the Russian 
scientists. 
