Porter — Relation of Growth to Probable Deviation. 237 
**schied also in der Grésse der Individuen immer merklicher 
‘*hervortreten lassen. Auch hinsichtlich der Geschlechter ist 
‘*‘ein Unterschied deutlich bemerkbar und zwar zeigen sich 
‘* fir die Madchen vom 11 Jahre an gréssere Schwankungen 
‘‘als fiir die Knaben. Da aber beobachtet worden ist, dass 
‘©die Madchen circa zwei Jahre vor Eintritt der Pubertiats- 
** periode verhaltnissmassig rascher wachsen, so diirfte die 
‘* Verschiedenheit, mit welcher der Eintritt dieser Zeit erfolet, 
‘* wohl ein Grund mit sein fiir die grésseren Schwankungen.”’ 
It appears from this extract from the valuable work of 
Geissler and Uhlitzsch that they were very near discovering 
the law which it is the purpose of this paper to demonstrate 
and would certainly have done so had they not contented 
themselves with the Absolute Probable Deviation, in which 
the real Physiological Difference of Individual from Type 
lies hidden, and had the material furnished them been 
sufficiently extensive. The Absolute Probable Deviation is 
entangled with the size of the individual, and its true value 
can be known only when this disturbing factor is removed. 
It is the relation between Probable Deviation and size of 
individual that must be studied, if the character of the 
Probable Deviation would be known. But even if Geissler 
and Uhlitzsch had pursued the method just suggested, the 
limitations of their material would have prevented them from 
solving the problem completely. For the material given 
them to analyze extended no further than the fourteenth year, 
with some observations over, almost wholly missing the 
period of pre-pubertal acceleration in boys and the early 
pubertal years in girls and entirely omitting the early pubertal 
years in boys. 
It would seem from their results that the Probable Devia- 
tion increases with the age, whereas it shall be presently shown 
that the Absolute Probable Deviation in height standing as 
well as in weight, height sitting, span of arms and girth 
of chest does not increase with age during the whole period of 
growth. Moreover, the Relative Probable Deviation does not 
increase during seven of the nine years of boys’ growth and 
five of the nine of girls’ growth included in the observations of 
Geissler and Uhlitzsch, and shows a merely secondary relation 
