PHENOMENA OF FLIGHT IN TTJV AxiTArAr 



uiii IN THE ANIMAL KINGDOM 255 



nuiii verj shorl^ ^^ '"°^' ''^^^^ the ster- 



ol , A -"I'-'^'^^'-'u lu Lue extent of 

 that surface; other tliiugs 1 eiifi 

 the same, a greaterexertron Is re" 

 quired to move a hir-e win ' than 

 one of less superficial elctent 



that the difierence in the form 

 of the pectoral muscles iu differ^ 

 eut birds accords with the diflbr- 

 euces presented in the manner 

 m ^hich thej perform their re 

 spective work. Two birds of the 



iaboi m flyiuo-, ^nd apparentlv 

 should have muscles of the same 



wht^. I 7^ thtterences in form 

 tTV J^ ^^ ^'^^^e indicated, we see 

 Uiattheworkisdoneindifferln? 

 wa s _ The birds with small 

 ^Jiigs increase the small resist 

 aoce which these offer to tlie ah- 



But, It ma.Y be said mtnvr. 

 might have attained tl e:se liffbr 

 ent methods of flight bv gh^cr 

 muscles of uniform%roani?al "S 

 toall birds. It would have beeu 



snftcient to have given difent 

 pasitions to the point of attach- 

 ment of the great pectoral to the 

 humerus, or, in other words to 

 vaiy the length of the arm of the 

 res stance. Comparative anat- 



ral is always attached close to 



Jifi "^?^"^^ (distance .Miich sep- 

 arates tins attachment from the 

 center of motion of the hurerus 



with the form of the bird and 

 not according- to the rela ive v 

 greater or less extent of thi 

 wing-s. This last depends prince 

 ??i^/"^»,,^^^^l^"8thofthefoi"- 

 aim and its appendages. It is 



Kls^of dT^ to dissl^ct many 

 f]il/^'^^''^^t kinds to prove 

 the constancy of the law which I 



