. Animal flight; a record of observation . B. During full-dip. C. During double-dip. but to a less extent (fig. 16). I have been able tosee this steering effect on several occasions, but perhapsmore often than not the effect is too small to be detected. It may be suggested that during a dip the air actsas a drag by pressing the upper surface of the suggestion is an easy explanation of the steeringeffect. But the phenomenon of the half-dip suggeststhat it is not sufficient, and facts to be described inlater chapters will be found to prove that a more deep-seated action is involved.
. Animal flight; a record of observation . B. During full-dip. C. During double-dip. but to a less extent (fig. 16). I have been able tosee this steering effect on several occasions, but perhapsmore often than not the effect is too small to be detected. It may be suggested that during a dip the air actsas a drag by pressing the upper surface of the suggestion is an easy explanation of the steeringeffect. But the phenomenon of the half-dip suggeststhat it is not sufficient, and facts to be described inlater chapters will be found to prove that a more deep-seated action is involved. ANIMAL FLIGHT. 73 The chief muscles concerned in rotating the wing-tip are shown in fig. 17. This is a diagrammatic viewof the under side of the wing, in which various musclesnot concerned with wing-tip rotation have been removedfor the sake of clearness. The following are the namesthat I propose for the muscles, with a short description : AIMd ShJ. Fig. 17. Dissection of right wing of Common Vulture (Pseudogypsbengalensis) seen from below, showing muscles concerned in rotation of wing-tip. ShJ. Shoulder joint. H. Humerus. EJ. Elbow joint. R. Radius. U. Ulna. CJ. Carpal joint. C. Carpal bone. Mcl. Metacarpal of Digit I. McII. Metacarpal of Digit Metacarpal of Digit III. Al. Alula or Digit I. Hp1. Basal or first phalanx ofDigit II. Hp?. Terminal or secondphalanx of Digit of Digit longus musclePronator phalangis muscleAbductor pinnae metacarpi muscleSupinator , II., III., IV. Digital , VI., VII., VIII., IX., X. Meta-carpal , S., S, Secondary quills. br. I. Pronator phalangis. This muscle arises fromnear the base of the ulna. Its tendon is inserted on thebase of the terminal phalanx of digit II. It may beexplained that the wing of the bird contains the remainsof three digits. Digit I. is known as the alula or bastardwing. The
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