Animal Morphology. 113 



and with that limb is combined motion that propels the 

 head in advance of the location in which the fish was, before 

 such motion commenced. 



In the motion of the fish the greatest power of resistance 

 is towards the head, in the direction of the great premo- 

 tionary sense sight, which sense, in relation to comparative 

 or gradational anatomy, is next in order to the sense of 

 want, or the par vagum. 



Again, the greatest proportion of weight is anterior to the 

 tail or posterior limb, so that propulsion has weight in 

 advance of the propelling power. 



Birds have the same peculiarity, for the greatest weight is 

 anterior to the axis of their motion, or combined result of 

 musciilar motion. It is scarcely fair to mention it, but this 

 was first arrived at by experiments, not upon birds, but upon 

 one or two foolish Cheiropterae, which were led astray by 

 white traps. Till then no trouble existed as to the way of 

 the eagle in the limpid air, neither had the Duke of Argyle 

 written at that time upon this elegant and beautiful subject, 

 and made it popular. 



The experiments were conclusive and decisive. The 

 upshot of the whole matter was this wing action was so 

 arranged, that force from the motion of air by muscle 

 was backwards, and that it was greater than the gravity 

 placed in front of it. Hence the head of the bird moved 

 in advance so much every motion of the wings. 



When birds swim, and when they walk, the gravity is 

 greatest in front of the axis of muscular motion, which is 

 near to the sacro-vertebral articulation ; when walking the 

 toes are anterior to the axis of gravity, as also in running; 

 but the axis of muscular motion is between the joint (as of 

 the hip or acetabulum) and the sacro-vertebral articulation, 

 and very slight adjustments of the axis of gravitation deter- 



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