1011] nn Biology and the CiiiematofjrapJt. 177 



by means of a small piece uf tissue paper. When full speed of the 

 wheel is attained, and when the insect — already placed in the tube — 

 moves forward in the tube towards the light and opens the swing 

 door, the paper falls and the electric circuit is made. By an ingenious 

 arrangement the shutter is placed in this circuit so that the insect 

 automatically opens and closes the shutter, and as it passes across 

 the field of the stereoscopic camera — a distance of a little over a foot 

 — impressions of the phases of its transit can be taken at the rate of 

 two thousand impressions per second. 



M. Bull has also photographed the passage of a bullet through 

 a soap bubble. The air gun used to propel the pellet is placed in 

 circuit with the shutter used for the exposure of the moving pellet as 

 it traverses the soap film. 



Through the kindness of M. Bull I am able to show you a beautiful 

 film of the flight of a dragon-fly and also of a blue-bottle taken by 

 means of his method. 



Merhanical a/n/ Chemical /Stimulation of a Reflex Fro//. 



A film of a " reflex frog " — i.e. an animal in which the brain is 

 destroyed, but still retaining its spinal cord — was shown, to illustrate 

 a reflex unilateral motor act in response to a mechanical stimulus of 

 the skin of one leg. To contrast with this striking unilateral 

 response, the extensive responses that occur in a similar frog where 

 the stimulus is chemical in its nature — viz. the application to the 

 skin of a small piece of paper dipped in dilute vinegar — was shown. 

 By adaptive " purposive " movements, the animal succeeded in 

 removing the offending object — a good example of a protective 

 reflex act or motor response. By means of a metronome beating 

 sixty times per minute and placed alongside the suspended frog, the 

 audience could determine the time the frog took to dislodge the 

 offending object. 



Sjwead Reflex of the Turkey Cock. 



The •• spread reflex " of the turkey cock described by L. Hill was 

 shown : — 



" If a turkey cock is placed sitting on a narrow stool and the 

 wings are sharply drawn downwards and forwards, the tail is spread. 

 This can be repeated as often as one likes, the animal behaving in 

 this respect like a mechanical doll. The same thing happens when 

 the turkey is standing, but in this case the disturbance of balance 

 which occurs on pulling down the wings somewhat lessens the 

 effectiveness of the spread of the tail. On lifting up and spreading 

 the tail, there occurs no reflex movement of the wings. The reflex 

 only works one way." (March 1910.) 



Vol. XX. (No. 105) n 



