DR PETTIGREW ON THE PHYSIOLOGY OF WINGS. 373 



falling of the weighted handle will have the effect, in conjunction with the 

 resistance which the under concave surface of the umbrella experiences from 

 the air, of opening it up, precisely as the wings are opened up and elevated at 

 figures 13, 14, and 15, Plate XIII. And if it so happens that the steels of the 

 umbrella are feeble, and the weight attached to the handle sufficiently great, 

 the umbrella will be more or less everted, as shown at 2, 2' and 3, 3' of figure 

 18, Plate XIV. If the frame of the umbrella was endowed with vitality, and 

 had the power of quickly regaining its original form, it would elevate the 

 weighted handle, and so attain its original position. A repetition of those 

 changes, if the proper degree and kind of power were added, would result in 

 flight, particularly if one side of the umbrella was rendered more rigid than the 

 other, as this would have the effect of conferring an eccentric action upon it. 

 The parachute principle here advocated is corroborated to a certain extent by the 

 flight of the beetles. In these, in some cases, the elytra or wing cases are deeply 

 concavo-convex. The membranes or true wings strike in a downward, forward, 

 and more or less horizontal direction, and in so doing they force the air forward 

 under the ventral or concave surfaces of the elytra or false wings, which are thus 

 converted into parachutes or tiny sustaining balloons. That the elytra perform 

 a very important function in flight is proved by the fact that when they are 

 removed the insect cannot fly. I had ocular demonstration of this at Somerton, 

 Wexford, in the summer of 1868. When I amputated the elytra close to the 

 roots, the insects could not rise, although they made frequent attempts to do 

 so. The elytra or false wings and the membranous or true wings form, when 

 extended, deeply concave or umbrella shaped surfaces, the peculiarity in such 

 instances being that the umbrellas formed by the true wings move and are 

 active ; whereas those formed by the elytra are fixed or immobile, and conse- 

 quently passive. 



The Wing of the Bird elevated as a Short Lever. — In birds with short rounded 

 wings, and in others with longer wings, in forced flight the wing is usually 

 elevated as a short lever, as shown at 6 of figures 6 and 19, Plates XL and 

 XIV., and 1 of figures 5 and 18, Plates XL and XIV. ; it being extended or 

 spread out quite towards the end of the up stroke, as represented at 1, 2, 3 of 

 figures 5 and 18, Plates XL and XIV. In birds with long pointed wings, when 

 flying leisurely, the wing is not unfrequently expanded at the middle of the up 



nate play of the feet. "What strikes one in the present woodcut is the comparatively small size of the 

 diving or swimming wing, which resembles the nipper of the turtle, seal, sea bear, and walrus. At 

 Plate XIII. figure 15, the aerial wing, as seen in the gull, is represented, and the large size of the 

 flying pinion, as compared with the diving subaquatic one, is at once apparent. Here the anterior 

 margin (x s t v w) of the wing is directed upwards and forwards, the posterior one (o p q) downwards 

 and backwards. This causes the under or ventral concave surface of the pinion to look downwards and 

 forwards, the direction in which the effective or down stroke is delivered. The aerial wing, like the 

 subaquatic wing, is twisted upon itself. It strikes downwards and forwards, because this is the direc- 

 tion in which a body in motion would naturally fall. 



