Aërial locomotion : Pettigrew versus Marey / by Professor Coughtrie.

  • Coughtrie, Millen.
Date:
1875
Catalogue details

Licence: Public Domain Mark

Credit: Aërial locomotion : Pettigrew versus Marey / by Professor Coughtrie. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    Marey, is the reply, claims to have been the first'to describe and illustrate the following;— I. That quadrupeds walk, and fishes swim, and insedts, bats, and birds fly, by Jigw'c-of-8 movements. 2. That the flipper of the sea bear, the swimming wing of the penguin, and the wing of the insedl, bat, and bird, are screws structurally', and resemble the blade of an ordinary screw propeller. 3. That these organs are screws ftmclionally, from their twisting and un- twisting, and from their rotating in the direction of their length, when they are made to oscillate. 4. That they have a reciprocating adlion, and reverse their planes more or less completely at every stroke. 5. That the wing describes a figurc-of-Z track in space, when the flying animal is artificially fixed. 6. That the wing, when the flying animal is progressing at a high speed in a horizontal diredlion, describes a looped and then a waved track, from the fadt that the figure of 8 is gradually opened out or unra- velled as the animal advances. 7. That the wing acts after the manner of a boy's kite,'''' both ' during the down ' and the ^ up ' strokes.* Such are bi-iefly Dr. Pettigrew's views; and if we com- pare what Professor Marey has written on flight with what Dr. Pettigrew here enunciates, we shall find the coincidences (to use no stronger terms) very striking. Take the following passages from Professor Marey's recent work as examples :— If we gild a large portion of the upper surface of a wasp's wing, taking precautions that the gold leaf should be limited to this surface only, we see that the animal placed in the sun's rays gives the figure-of-8 with a very unequal intensity in the two halves of the image It is evident that the cause of the nhenomenon is to be found in a change in the plane of the wing, and consequently in the incidence of the solar rays We shall find in the employment of the graphic method new proofs of changes in the plane of the wing during flight [In this and other quotations the italics are ours.] It is therefore not necessary to look for special muscular adlions to produce changes in the plane of the wing ; these in their turn will give us the key to the oblique curvilinear movements which produce the figure-of-8 course followed by the inseft's wing.—(Animal Mechanism, pp. 188, 197). In the passages here cited, Professor Marey admits, not only that the wing of the insecft makes a figure-of-^ track in space, but also that the figure-of-8 is produced by a change of plane in the wing. This is an important admission, for Professor Marey copies at page 201 of his book a figure-of-8 representation from Dr. Pettigrew's 1867 memoir,t in which this change of plane is delineated, and states that the arrows in Dr. Pettigrew's figure all point in one direction, and are wrongly • On the Physiology of Wings. By J. Bell Pettigrew, M.D., F.R.S. Trans. Roy. Soc. of Edinburgh, vol. xxvi., p. 332. ^ t Marey's figure is Fig^ 86, Trajecftory of the Wing, p. 201. Pettigrew s figure is at p. 233. Trans. Linn. Soc, 1867., vol. xxvi.