78 FROM FISH TO PHILOSOPHER 



to one or several hours. The heart slows to perhaps only 

 three beats per minute and, except for the infrequent 

 pulse and respiration, the animal appears to be in a 

 state of suspended animation. 



In captivity the lungfish Hes quietly on the bottom of 

 the aquarium or leans lackadaisically against the side, 

 moving only to eat or breathe. For the latter purpose it 

 need only flex its body and swim gently to the surface, 

 where the lung is quickly emptied and filled again with 

 air. But it is nevertheless a conscious animal, aware of 

 its environment and of itself. However, when removed 

 from its mud block after several months of estivation, it 

 is as dormant as a sleeping child. One may debate if 

 one can properly speak of 'sleep' in the lower animals— 

 we do not know what sleep is in the higher animals 

 except that it appears to involve cessation of activity in 

 the higher nervous centers— but to use the word loosely, 

 insects 'sleep,' sometimes so soundly that they can be 

 picked up without disturbing them; fishes apparently 

 drowse off for a nap in a quiet corner or under a stone 

 (the mackerel is an exception in that it must keep swim- 

 ming in order to aerate the gills, so that if it sleeps it 

 does so while swimming), while reptiles, birds, and 

 mammals all have their periodic escape from conscious 

 Hfe. 



Whether the estivating lungfish is asleep or not is, for 

 the moment, a matter of a hairsplitting definition— it cer- 

 tainly is not conscious, as is the active animal when it is 

 searching for snails on the rocks and papyrus stems, or 

 following interestedly a piece of beef -heart dangled in 

 the aquarium by teasing fingers. When the cocoon is 

 peeled away, bit by bit, the fish is as moist as though 

 it had just been removed from water, but the body, 

 which gives off a pungent, never-to-be-forgotten odor, 

 is inert except for the fine twitching of a muscle fiber or 

 a sudden respiratory gasp, and it remains so for days or 

 weeks if kept in a moist chamber. This dormant state is 

 not attributable to lowered basal metabolism, dehydra- 



