EXTERNAL ANATOMY. SOANSOBIAL FEET. 141 
much more support backwards, in such a position, than 
any other birds. In order to effect this, nature has 
recourse, so to speak, to other means than those she 
usually employs. The hinder toe and claw is either 
enormously developed, and tlie tail has no additional 
power given it (as in the case of Cliniacteris and Sitta), 
or, — if still greater support is necessary than would l)e 
acquired by this structure, — the tail itself, by a peculiar 
formation, is made to perform the same office as the 
hind toe, but with infinitely more effect. This brings 
us to the point at issue. The Sitta derives its sole sup- 
port when climbing from its posterior toe, which is conse- 
quently unusually large. Dmidrocolaptes, on the other 
hand, being a much more powerful and rapid climber 
(as we have proved by the structure of its anterior 
toes, and have witnessed by personal observation), 
requires a much greater support backwards, propor- 
tionate to its power of advancing forwards. 1 he tail 
is, therefore, enlarged and strengthened in such a way, 
by rigid points which stick into the bark, that the office 
of the hind toe is almost superseded, and its size is 
consequently not greater than in the generality of birds. 
VTe should not have gone into these explanations merely 
for the purpose of refuting the sort of criticism to 
which on another occasion we have been exposed*, hut 
because they will deter the young ornithologist from 
forming hasty judgments iqjon matters which more ex- 
tended investigation would place in a different light. 
These details will also demonstrate, what is of far 
greater interest, another and a new proof of that har- 
mnny of design, and that infinite “diversity of ojk-- 
rations “ which the Infinite Beino has manifested in 
these his glorious, yet lower, works. 
(124.) There are yet three other modifications of 
the scansorial foot which must not be passed over. 
* Vide tbe periodical critics, on the Preliminary tTisconrse. The 
of our readers who may possibly be influenced 'ueh mi_sre|>iTO^^l‘^ 
and falsehoods, will Hnd them very neatly exposed in the 1-nt K 
Magazine ” tor April, lS3o. 
