228 MOVEMENT 



so that the bird could fly freely about in a large room. 

 The descent of the wing closed the current, and during 

 its ascent the current was broken, so that each flap of 

 the wing left a mark on the cylinder, just such as 

 that caused by the rise and fall of a man's foot in 

 walking. 



By counting on the tracing the number of ascents 

 and descents executed by the wing in a given time, 

 the frequency of wing movement proper to each species 

 could be obtained with the greatest exactness. 



It will be noticed that, following the general laws 

 applicable to living beings, the smallest birds have 

 the most rapid movements ; the sparrow giving twelve 

 strokes to the second, the pigeon eight, and the 

 buzzard three. The relative duration of the rise and 

 fall of the wing can be measured by means of the same 

 chronographic tracing. These two phases are of un- 

 equal duration, especially in the case of large-winged 

 birds, the duration of descent being considerably 

 longer than the period of ascent. This is entirely 

 contradictory to all preconceived notions.* 



Registration of Muscular Actions. — Mechanical regis- 

 tration is the only means we have at present for 

 determining the phases of contraction and relaxation 

 of the wing muscles. A pigeon (Fig. 159) is provided 

 with a closely fitting corset, under which is slipped 

 a " myographic capsule," which is arranged so as to 



* " By means of this method we have been enabled to demonstrate 

 experimentally one of the most important points in the mechanism of 

 flight, namely, that the wing meets with greater resistance from the 

 air the mure rapid the progression of the bird. It appears that if a bird 

 is travelling at a certain rate it continually comes in contact with fresh 

 resistance from the air, and it is the inertia of these new masses of 

 air which has constantly to be overcome. On the other hand, if the 

 bird is stationary when it takes a stroke witii its wings, the air which 

 is struck disappears from under the wing and offers no more resistance. 

 Hence it is that if a bird intends to take flight, it first tries to acquire 

 a certain velocity, either by taking a run, or by dropping a certain 

 distance from an elevated position."— Le Vol desOiseaux, p. 249. 



