254 



ANIMAL MECHANISM. 



assistant, may be considered as horizontally extended, tending 

 neither forwards nor backwards. This line represents, there- 

 fore, to some extent, the zero of the scale of the movements 

 of the wing in its anterp -posterior direction. The inspection 

 of the curve shows us also, that the pigeon's wing was carried 

 more especially in the direction of the upper parts, similar to 

 the point A ; in other terms, that the forward predominated 

 over the backward movement. 



ana 



1 



■ 



MM 



1 



m 





H 





1 

 1 

 1 



1 

 1 



1 



i 



I 



1 

 1 

 1 

 1 



m 



m 



n 

 ■i 



11 



■ 

 ■ 



■ 



Hi 

 ■I 



Fig. 106. — Superposition of the preceding curves on paper divided in milli- 

 metres. The two curves have a common direction with reference to the 

 axis of the abscissae. 



The same explanations would apply to the lower curve 

 H P, which expresses the movements of the wing upwards 

 and downwards. 



In order to ascertain if the course of the pigeon's wing in 

 the present experiment is apparently the same as that of the 

 buzzard recorded before, we have constructed the complete 

 curve of the wdng during one of its revolutions, making use 

 for this purpose of the two partial curves of fig. 105. 



The following is the method employed in this construction : 



In order to give more facility to the measurement of the 

 positions of the different points of these curves, we have 

 copied them both on a paper graduated in centimetres and 



