BEHAVIOR OF VERTEBRATES 439 



TASTE 



Amphibia. Cole ^■'' suspended fresh, brainless frogs from a 

 hook on lever device and dipped their hind feet into given solu- 

 tions of chlorides of ammonium, potassium, sodium, and lithium. 

 After a variable time the frogs withdrew the feet from the solu- 

 tion. The time of the reaction (from the moment of immersion 

 to the moment of withdrawal) was taken with a stop-watch 

 in seconds and fifths of seconds. The reaction times of the 

 frogs to 3m., 2m., im., and m/2 solutions of these chlorides 

 gave grounds for " distributing these salts into two groups — 

 ammonium and potassium ; sodium and lithium, an arrangement 

 already indicated by their degree of concentration." The most 

 rapid reaction occurred with the chlorides of greatest dissocia- 

 tion. It is suggested that the total reaction time includes two 

 factors: diffusion time and summation time. 



On the question of the receptors involved in the reaction 

 Cole suggests without sufficient evidence that " the comparisons 

 with the tastes of chlorides of these metals and the results of 

 applying cocaine, suggest that nerves of a general chemical 

 sense rather than pain nerves are affected by the chlorides." 



EXPERIMENTAL AND OBSERVATIONAL STUDY OF INSTINCTS 



Mammals. Yerkes and Bloomfield ^'^ have made an interest- 

 ing ^et of observations upon two litters of kittens, to test the 

 definiteness of their instincts for catching and killing mice. It 

 will be remembered that C. S. Berry, a few years ago, reported 

 from his observations upon a litter of Manx cats that " cats 

 are credited with more instincts than they really possess. It 

 is commonly reported that they have an instinctive liking for 

 mice, and that mice have an instinctive fear of cats. It is sup- 

 posed that the odor of a mouse will arouse a cat, and that the 

 odor of a cat will frighten a mouse. My experiments tend to 

 show that this belief is not in harmony with the facts. When 

 cats over five months old were taken into the room where mice 

 were kept they did not show the least sign of excitement. A 

 cat would even allow a mouse to perch upon its back without 

 attempting to injure it. Nor did the mice show any fear of the 

 cats. I have seen a mouse smell of the nose of a cat without 

 showing any signs of fear." Berry concludes finally that it is 

 through imitation that the average cat learns to kill and eat mice. 



