LITERATURE FOR 1911 ON THE BEHAVIOR OF 

 VERTEBRATES 



JOHN B. WATSON 



Johns Hopkins University 



VISION 



Fish. C. Hess (13) offers a new piece of apparatus for the 

 study of adaptation in fish. At one end of a dead black tunnel 

 three metres in length he places a five candle power electric 

 light with frosted bulb. At the opposite end of the tunnel and 

 inclined at an angle of 45 degrees to its axis he places a diffusing 

 surface of ground glass. The light from this surface is reflected 

 out to a dish which contains the fish. Large changes in intensity 

 are made by substituting lamps of higher or lower candle power, 

 while fine gradations are obtained by the use of the rotating 

 sector and by moving the lamp. The animals are light-adapted 

 in the sun and then quickly placed in the experimental tank. 

 The animals respond by swimming towards the side of the tank 

 receiving the rays from the ground glass as soon as the process 

 of adaptation is sufficiently advanced. For example, the carp 

 exposed to the rays of the sun for one-quarter of an hour, show 

 in the first second of time no tendency to swim towards the 

 light when the 5 c.p. light is 30 cm. from the ground glass. 

 After 20-30 seconds in the dark room, they swim toward the 

 lighted side when the lamp is moved back 1-2 metres. After 

 10-15 minutes adaptation, they swim towards the light when 

 the lamp is 3 metres distant from the screen and the rotating . 

 sector set with a 30 degree opening. He concludes that light 

 sensitivity is increased over a thousand fold after fifteen minutes 

 of adaptation. In some cases even a greater increase in sen- 

 sitivity is found. 



He finds an essential difference between the human and the 

 fish eye. In man the retinal pigment even in long exposure 

 to light does not essentially change its position, while in the 

 case of the fish the pigment upon light exposure wanders soon 

 toward the vitreous humor. This may offer a physical expla- 



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