604 MUSCOLAKY SYSf LAT 
and ultimately lost, its so-called “long flexor” muscle would in all 
likelihood disappear also, because in existing Passeres its tendon 
is unconnected with that of the M. flexor perforans digitorum, 
while Birds which lost the hallux before these two tendons were 
disconnected have kept both these muscles. 
Prof. Fiirbringer, who with enormous labour has exhaustively 
studied the muscles of the shoulder-girdle, has tabulated the 
chief characters of 14 muscles selected with a view to taxonomic 
application, but the results are very small and far less obvious 
than those afforded by the muscles of hind limbs. The former, 
as the apparatus of Flight, seem to be more uniformly constructed 
than the latter, which are more diversified according to the varied 
uses of the legs and feet. Fluttering, skimming, sailing, soaring 
are motions much more akin to one another, than climbing, grasp- 
ing, running, scratching, swimming and wading. ‘The only really 
aberrant modifications of the wings and their muscles are found in 
the Ratitz, where they are all easily explained by reduction, and 
in the Spheniscidy, where bones and muscles are greatly specialized. 
The modifications of the hind limbs are many times greater—such 
as extremely long legs, with four, three or only two toes—short or 
long: very short legs, almost incapable of running or walking, with 
all four toes directed forwards, or two or one backwards, and two 
or more connected in various ways. 
Most Muscles leave an impression upon the bones to which 
they are attached, in the shape of ridges, furrows, crests and 
processes. These marks, small as they often are, are mostly 
significant, and of greater assistance in the recognition of a bone 
than its general configuration, as any one will find on trying to 
determine the’ kind of bird to which a given bone belongs. The 
muscles are not as a rule attached to such crests and ridges 
because these happen to be there, but on the contrary they shape 
the bone which serves as their passive framework : what is bred in the 
flesh comes out in the bone, not vice versd. It is the quality not 
the quantity of an organ that determines its taxonomic value, 
and adhesion to this principle precludes us from classifying Birds 
by trim myological formule which seem to afford easy keys, but 
rather obscure than elucidate natural affinities. 
Without entering upon genetic and therefore fundamental 
differences, the voluntary skeletal muscles may be conveniently 
grouped thus :— 
A Muscles supplied by spinal nerves. 
a. Muscles of the Stem (neck, trunk and tail). 
1. Dorso-spinal Muscles, supplied by dorsal branches. 
2. Ventri-spinal Muscles, supplied by ventral branches. 
B. Muscles of the extremities (limbs) supplied by ventral 
branches. 
