To say that a lower animal such as a crab can- 

 not suffer pain, is to utter nonsense. Still this 

 superstition does prevail, even among some in 

 whom, by their learning and attainments, one 

 might expect maturer convictions. Pain is the 

 alarm signal of the organism. It is through this 

 medium that danger to the tissues is apprehended. 

 However, from what is known of the functions of 

 the nervous system in invertebrates, it is not un- 

 likely that the more lowly organized is the crea- 

 ture, the less sensitive it is to those injuries that 

 cause pain in man and other mammals. Thus a 

 worm or crustacean will probably suffer less than 

 a human who is also constituted so that his suffer- 

 ing is accompanied by an intense psychic dis- 

 turbance. Moreover, the purpose of pain being a 

 warning, its presence in any creature would seem 

 to be in proportion to that creature's power of 

 regeneration. In other words, a primitive creature 

 such as can grow new organs or other parts with 

 facility is less likely to feel physical pain than 

 higher animals not so endowed. To a starfish or a 

 sea-anemone, both of which have a low nervous 

 system, it is of little consequence to be cut com- 

 pletely in two: such an injury to the more highly 



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