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THE AMERICAN NATURALIST 



[Vol. L 



structure of the organism is the important cause of the 

 lethargy; but it acts as a mechanism of economy by in- 

 creasing the resistance of the animal to cold, rather than 

 to starvation, and thus prevents histolysis from reaching 

 a dangerous point. An inefficient heat-regulating mech- 

 anism has been considered the true explanation of winter- 

 sleep by such men as Duges 24 (1838), Mares 42 (1889), and 

 Polimanti 43 (1904). Simpson 44 (1911) in this laboratory 

 has shown that the woodchuck can not be said to ever 

 have a normal temperature in the sense that a homoio- 

 thermal animal has. Merzbacher 40 (1904) cites many 

 cases similarly indicating the weak thermogenic organi- 

 zation among winter-sleepers. Eecently Polimanti 45 

 (1914) has explained his views concerning this labile 

 thermogenic organization. To him it is due to the fact 

 that at some remote period all animals then existing 

 periodically fell into lethargy. With evolutionary de- 

 velopment most mammals and all birds lost this ability. 

 Hibernating animals, however, are still able to return to 

 this cold-blooded type when the heat-producing reflexes 

 fail, which they are apt to do when the cold becomes ex- 

 treme. Mares 46 (1913) holds fundamentally this same 

 view— a view he advanced in 1889. He says that the 

 cause of hibernation is in the organism itself. He re- 

 gards the facts presented by Pembrey 47 and Babak 48 and 

 others concerning the poor heat-regulating mechanism of 

 the newborn in man and other animals, as well as those by 

 Merzbacher 49 on the return of the nervous system to a 

 more segmental type during winter-sleep, as strong evi- 

 dence in favor of the theory, and as indicating that hiber- 

 nating animals merely revert to a more primitive type in 

 which there is no specific sensibility to the outer cold, i. e., 

 in which no specific heat-regulating reflexes are called 

 forth by the external temperature. He further thinks 

 that since the weakness is in the nervous system, it ought 

 to be possible to bring about some of the conditions of 

 torpor by means of hypnotic suggestions. He and Hel- 

 lich 50 (1889) succeeded by this means in getting a fall of 



