144 BIOLOGY. [Book ii. 



animals, normally muddy and alkaline, becomes clear and acid 

 like that of the carnivorous animals. Besides, if we compare 

 each day the quantity of oxygen absoi'bed by an animal in a 

 state of inanition, by respiration, with the quantity of the same 

 gas which enters into the composition of the carbonic acid 

 exhaled, we see the proportion established first of all as if the 

 animal had been subjected to an alimentation of fat, then as if 

 it had been exclusively nourished on animal food, but in an 

 insufficient quantity.^ 



In effect, assimilable, complex, ternary, and quateiiiary sub- 

 stances are ^necessary to the anatomical elements of animals ; 

 but it matters very little whether these substances are derived 

 from the vegetal kingdom or the animal kingdom, provided they 

 have undergone a suitable preparation. If these aKments of 

 exterior origin fail, the nutritive movement continues never- 

 theless fox a longer or shorter time in complex animals, but 

 then it is exercised at the expense of the living substance itself ; 

 the organism literally eats itself. The blood first yields all that 

 it can yield of assimilable substances, and repairs its losses at 

 the expense of the tissues, and of the anatomical elements, of 

 which it previously furnished the materials. It takes back 

 what it gave. This is called physiological abstinence. 



This abstinence may be provoked by various causes. Every- 

 thing which can disturb the' internal mutations of the tissues in 

 such a way as to cause the nutritive expenditure to predominate 

 over the receipts is a cause of physiological abstinence; for 

 example, an ill-chosen alimentation, even if it be copious, to 

 which is wanting any one of the constituent principles indis- 

 pensable to the organism ; or an incomplete reparation, whether 

 it be a pathological defect of the organs, or an alteration of the 

 exterior air (encumberment, confined air, etc.). Abstinence beai's 

 simply upon the oxygen then ; but we have seen that this gas 

 is indispensable to the utilization of alimentary materials. 



In the lowest scale of the organized world, in beings formed of 

 ^ G. See, Le Sang et les Animies. 



