362 



DB, PETTIGKEW ON THE PHYSIOLOGY OF WINGS. 



Curves in all respects analogous to those occurring in the wing of the butterfly 

 and dragon-fly are observed in the wing of the bat and bird, as a reference to 



Fig. 39. 



Fi°r. 40. 



Fig. 41. 



Fig. 42. 



Fig. 43. 



figs. 39, 40, 41, 42, and 43 will satisfy. They are also found in the rowing- 

 feathers of the wing of the bird, as shown at fig. 50, page 379. 



4. Eeinoved the posterior -wings of the brown butterfly. Flight unimpaired. 



5. Kemoved in addition a small portion (one-sixth) from the tips of the anterior wings. Flight 

 still perfect, as the insect flew upwards of ten yards. 



6. Eemoved in addition a portion (one-eighth) of the posterior margins of anterior wings. The 

 insect flew imperfectly, and came to the ground about a yard from the point where it commenced its 

 flight. 



7. In the dragon-fly either the first or second pair of wings may be removed without destroying 

 the power of flight. The insect generally flies most steadily when the posterior pair of wings are 

 detached, as it can balance better ; but in either case flight is perfect and in no degree laboured. 



8. Eemoved one-third from the posterior margin of the first and second pairs of wings. Flight 

 in no wise impaired. 



If more than a third of each Aving be cut away from the posterior or thin margin, the insect can 

 still fly, but with effort. 



Experiment 8 shows that the posterior or thin flexible margin of the wing may be dispensed with 

 in flight. It is more especially engaged in propelling. 



9. The extremities or tips of the first and second pair of wings may be detached to the extent of 

 one third, without diminishing the power of flight. 



If the mutilation be carried further, flight is laboured, and in some cases destroyed. 



1 0. When the front edges of the first and second pair of wings are notched, or when they are 

 removed, flight is completely destroyed. 



This shows that a certain degree of stiffness is required for the front edges of the wings, the front 

 edges indirectly supporting the back edges It is, moreover, on the front edge of the wing that the 

 pressure falls in flight, and by this edge the major portion of the wing is attached to the body. The 

 principal movements of the wing are in addition communicated to this edge. 



Note. — Some of my readers will probably infer from the foregoing experiments, that the figure 

 of 8 curves formed along the anterior and posterior margins of the pinion are not necessary to flight, 

 since the tip and posterior margin of the wing may be removed without destroying it. To such I 

 reply, that the wing is flexible, elastic, and composed of a congeries of curved surfaces, and that so long as 

 a portion of it remains, it forms, or tends to form, figure of 8 curves in every direction. 



Figures 39, 40, 41, 42, and 43 si ow the double curves which occur on the anterior (bac) and posterior (dcf) 

 margins of the wing of the bat and bird. 



