PHENOMENA OF FLIGHT IN THE ANIMAL KINGDOM. 



275 



pens that the transmission is not equally good in both directions, which 

 is perceptible by the deformity of the transmitted figure, which is in- 

 creased more or less in height or breadth. This deficiency can always 

 be corrected, since it is due to the membrane of one of the drums being 

 stretched more than that of the other, and hence yielding less easily to 

 pressure. It is very easy to equalize the tension by tightening the mem- 

 brane of the other drum until the figure traced by the first lever is 

 identical with that traced by the second. 



The modifications by means of which I have rendered this trans- 

 mission applicable to the study of the motions of the wing of a flying 

 bird, are as follows : 



^ The apparatus 

 ■^ necessarily being 

 5 heavy, it required 

 •^ a large bird to carry 

 >> it. Stroug adult 

 ■g harriers served for 

 £ the experiments. I 

 g fixed a light strip 

 of wood upon the 

 "^ bird's back, upon 

 •^ which the api)ara- 

 1 tus was placed, by 

 G means of a kind of 

 i corset, which left 

 1 the wings and feet 

 free. That the le- 

 ver might faithfully 

 execute the same 

 motions as the 

 bird's wing, the 

 joint of the lever 

 should be placed 

 in contact with the 

 humeral articula- 

 tion of the harrier. 

 ^ As the presence of 

 S the drums by the 

 I side of the lever 

 g; does not permit this 

 ^ immediate contact, 

 ■z I had recourse to a 

 := parallelogram, 

 '$ which transmitted 

 ^ to the lever of the 

 ■?, apparatus the 

 movements of a 

 long arm of which 

 the center of mo- 

 tion was very close 

 to the articulation of the bird's wing. Finally, to obtain an identity of 

 motion between the arm and the harrier's wing, I fixed on the bastard 

 wing, that is to say, on the metacarpal portion of that organ, a well cut 

 screw-vise, furnished with a ring, through which passed the steel arm 

 of which I have just spoken. 



