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XV. — On the Physiology of Wings, being an Analysis of the Movements by 

 which Flight is produced in the Insect, Bat, and Bird. By James Bell 

 Pettigrew, M.D., F.R.S., Pathologist to the Royal Infirmary of Edinburgh, 

 and Curator of the Museum of the Royal College of Surgeons of Edinburgh. 

 Communicated by Professor Turner. (Plates XL to XVI.) 



(Received 2d August 1870. Read 16th January 1871.) 



INTRODUCTORY REMARKS. 



(For Table of Contents see end of Memoir.) 



In order to determine with exactitude the movements made by the wings in 

 flight, and the part which the air plays in modifying them, I was induced several 

 years ago to collect a large number of facts, and to undertake an extensive 

 series of experiments with natural and artificial wings. My observations and 

 experiments, I may remark, were not wholly confined to flight. On the con- 

 trary, I traced the analogy between flying, swimming, and walking ; a circum- 

 stance which compelled me to pay particular attention to the size, shape, and 

 movements, not only of wings, but also of the travelling surfaces of quadru- 

 peds, amphibia, and fishes. By adopting this method, I obtained suggestions 

 which have proved of the utmost importance to me in my attempts at elucidat- 

 ing the very intricate problem of flight. 



As there are, strictly speaking, only three highways in nature (the land, the 

 water, and the air), so there are three principal varieties of locomotion. There 

 are, however, a limited number of mixed forms, the animal in such cases being 

 furnished with travelling surfaces, modified in such a manner as to enable it to 

 progress upon, or in, two essentially different media. The mixed movements are 

 alike interesting and instructive, as they prove that movements apparently very 

 dissimilar are in reality only links of a great chain of motion, which drags its 

 weary length over the land, through the water, and extends skyward. That, 

 therefore, is not wanting which connects the motions peculiar to walking- 

 animals with those peculiar to swimming and flying animals. Thus the seal 

 furnishes the link between the land and water, and the galeopithecus between 

 the land and air ; while the flying fish supplies the link between the water 

 and the air. 



On making a careful examination of the structure and movements of the 



VOL. XXVI. PART II. 4 O 



