24 



ANIMAL MECHANISM. 



To this list of Hartings we will add another which we have 

 prepared by the same method (p. 225). All the experiments have 

 been made on birds killed by the gun, and a few instants after 

 death. We have taken the surface of the two wings instead 

 of only one, as Hartings had done ; this modification, which 

 appeared necessary, is the principal cause of the difference 

 which the reader will find between our numbers and those of 

 the Dutch physiologist. To compare the two tables, it will 

 be necessary to multiply by \/2 the number obtained by 



Hartings as the expression of the ratio -p 



The variations that we find in the ratio of the weight of 

 the body to the surface of the wings in different species of 

 birds, depends in a great degree on the form of the wings. 

 In fact, it is not immaterial whether the surface which strikes 

 the air has its maximum near the body or near the extremity; 

 these two points have very different velocities. For an equal 

 extent of surface the resistance will be greater at the point of 

 the \\ing than at its base. It follows from this, that two birds 

 of unequal suii'ai n of wing may find in the air an equal resist- 

 ance, provided that these surfaces are differently arranged. 



The weight of the pectoral muscles is, on the contrary, in 

 a Minplc rat in to tin- total weight of the bird, and imtwiih- 



