i EXCHANGE OF MATERIAL 17 



metabolism, one which should logically be studied before the 

 exchange which takes place on the introduction of various kinds 

 of food-stuffs. 



During a fast the animal organism takes in oxygen only, and 

 this serves for the combustion of the organic substances which 

 form the reserves stored up from past meals, or constitute the 

 living foundation. During fasting, therefore, there is no cessation 

 of consumption although no material for repair is introduced from 

 outside ; the result is a continuous loss of weight, which forms 

 the most obvious and invariable sign of the process of inanition, 

 during which the organism consumes itself, i.e. some elements of 

 its tissues, although to a very different extent in the different 

 tissues. 



The metabolism during inanition is a starting-point of the 

 utmost importance for the interpretation of the phenomena of 

 the normal exchange under different forms of nutrition, the 

 investigation of the extent of this exchange, and the de- 

 velopment of the theory of nutrition, the determination of the 

 alimentary needs of the organism under different physiological 

 or abnormal circumstances. 



We must first answer certain preliminary questions : How 

 does the power of resistance to inanition differ in various 

 animals ? How far is inanition compatible with life, and how 

 does it lead to death? Can the normal state of the most 

 important functions of the organism be preserved during fasting 

 for a certain length of time ? 



Experiments have shown that the power of resistance to 

 fasting is considerably greater in both men and animals than is 

 commonly supposed. The animal most frequently used in such 

 researches is the dog. Data supplied by various authorities 

 prove that the average duration of inanition in the dog is 33 days 

 (Richet). Adults have more power of resistance than the young, 

 fat subjects more than thin, the time varying from 20 to 60 days. 

 As a rule, carnivorous animals resist longer than herbivorous : the 

 cat 20 days, the rabbit 13 at most. Large mammals resist longer 

 than small ones, even when they are varieties of the same 

 species : the pig 34 days, according to Colin ; mice 2 or 3 days, 

 according to Redi, Colin, and others. 



The duration of inanition in birds is also considerable. For 

 the hen 14 days on an average, the pigeon 11, the eagle, according 

 to Buffon, 35 days. Cold-blooded animals stand inanition for a 

 marvellously long time : salmon 8-9 months, rattlesnake 27 

 months, python 23 months, the frog, chameleon, and salamander 

 12 months ; tortoise 18 months, viper 20 months. 



Hence there is a great difference in the duration of life in the 

 various classes and species of animals, and no small difference 

 even between individuals belonging to the same species. One 



VOL. v c 



