6o4 MUSCULAR SYSTEM 



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, seeci 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 Ratitse, where they are all easily explained by reduction, and 

 in the Spheniscidse, 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 versa. 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 formulae which seem to afford easy keys, but 

 rather obscure than elucidate natural afiinities. 



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 Lranclies. 



2. Ventri-spinal Muscles, supplied by ventral branches. 

 p. Muscles of the extremities (limbs) supplied by ventral 



branches. 



