8o8 THE POPULAR SCIENCE MONTHLY. 



tent, though it must be sufficient on the whole to balance waste. We 

 must not regard the object of food, however, as being merely to build 

 up the matter of the body ; we must rather consider it as intended to 

 recruit the energies of the body. The more active any creature is, both 

 in its automatic and its voluntary movements, the greater will be the 

 amount of hydrocarbons consumed or used up in its muscles, and the 

 greater, consequently, the amount of food and oxygen which it will re- 

 quire to make up the loss. The tiny humming-bird will need far more 

 food in a year than the great anaconda with which we began our dis- 

 course : because the humming-bird has a rapidly moving heart and lungs, 

 while the cold-blooded snake respires and circulates slowly ; and the 

 humming-bird darts about perpetually at lightning-speed from flower to 

 flower, while the snake lies coiled up motionless in its blanket from 

 year's end to year's end, or only comes out sleepily now and then to 

 swallow the food which will keep up its vital actions through another 

 long and lazy fast. 



The desert-snail, however, can endure much longer without food 

 than even the anaconda, because, like so many other moUusca, it can 

 hibernate. This process of hibernation consists in the inducement of 

 a state during which the heart ceases to beat, respiration is suspended, 

 and the animal can hardly be said to live at all. But when warmth and 

 moisture are once more applied, the heart recommences its action, the 

 lungs or gills quicken their movements, voluntary locomotion ensues, 

 and the creature sets out again en the quest for food. Something analo- 

 gous occurs in the case of the bear, the dormouse, and other hiber- 

 nating quadrupeds ; but in these instances the vital functions continue 

 much more in their ordinary state, and are kept up by the supply of 

 fat Mdiich is dissolved by the blood, and consumed in efi'ecting the neces- 

 sary automatic actions. The bear, which gees to sleep in the autumn 

 as sleek and plump as a prize pig, wakes up in the spring a poor, lean 

 wretch, with only just flesh enough to cover his bones, and carry him 

 ofi" in search of fresh food. The much more complicated mechanism of 

 the higher animals requires to be kept always in action ; it can not cease 

 almost entirely, like that of the snail, and then revive again when cir- 

 cumstances become more favorable. Hence hibernating mammals must 

 lay by fat during the summer to keep their principal organs at work 

 during the long winter fast. Yet, even among human beings, cases of 

 " trance " or " suspended animation " occasionally occur, during which 

 the cycle of vital actions almost entirely ceases to all appearance for a 

 considerable time, and then begins again on the application of some 

 external or internal stimulus — which latter may be not unaptly com- 

 pared to the slight shaking which we sometimes give a watch or clock 

 to set it going when stopped by a momentary impediment. Persons re- 

 covered from drowning, in whom the cessation of action has been quite 

 sudden and has not afi'ected the structure of their organs, are often thus 

 restored by the judicious use of rubbing and alcohol. 



