DISTRIBUTION OF MEMORY 231 



something similar in a small Crustacean, Gammarus, 

 during copulation. The abdomen of the male can be 

 cut off while it is seated on the female without caus- 

 ing it to release the female. In fact, unless my mem- 

 ory deceives me, these males without abdomen, when 

 torn away from the female, were ready to hold another 

 as soon as they could find one. Norman has added 

 a great many similar observations on insects and 

 Crustaceans (10). The result of all these observa- 

 tions is that either these Invertebrates do not react 

 to injury in a way which indicates the existence of 

 pain-sensation, or that, if there seem to be such re- 

 actions, they do not justify the assumption of the 

 existence of pain-sensations. 



We cannot be surprised that among those repre- 

 sentatives of the lower Vertebrates which have no 

 associative memory, or only traces of it, similar con- 

 ditions exist. 



Hermann and other physiologists maintain that 

 the reactions of lower Vertebrates under the influence 

 of an ascending current are due to pain-sensations, 

 while the descending current is said to have a sooth- 

 ing effect. Garrey and I came to the conclusion that, 

 in both cases, different sets of muscles were thrown 

 into activity (see Chapter XL). In order to test 

 Hermann's view, we experimented on larvae of Am- 

 blystoma whose spinal cord had been cut between the 

 head and the tail-end of the body. We found that 

 in the ascending current only the tail-end of the ani- 

 mal showed those reactions which Hermann and the 



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