220 MANUAL OF CATTLE-FEEDING. 



all blood by injection of a weak solution of salt, will con- 

 tinue to beat for hours, and the whole aninial, under the 

 same cii^cunibtances, moves, leaps, and behaves in short 

 like a living animal. Agassiz relates that on one occasion ^ 

 he captured a shark, which fought as long and fiercely as 

 is usual with these animals, but which, when finally se- 

 cured, was found to have its gills eaten through by para- 

 sites, and almost all its blood replaced by sea-water. 

 (Liebig.) 



In cases like these, the products of the muscular action 

 being continually removed by the salt solution, etc., the 

 muscles may continue active until their store of force is 

 exhausted. Like a bent spring, the muscle contains a cer- 

 tain amount of potential energy, which the will can use at 

 pleasure ; but when the supply is once exhausted, when the 

 spring has lost its tension, a f mother supply of force from 

 without is necessary before more work can be performed. 



We have to consider, then, in what manner and by 

 means of what substances this storing up of energy takes 

 place. 



Storing up of Oxygen. — It would appear that the 

 storing up of oxygen in the body which has been shown 

 by Pettenkofer & Voit and by Ilenneberg (see pp. 85-8^) 

 to take place under certain circumstances, is connected with 

 the storir>g.p of energy. 



In the following tables are given the amounts of car- 

 bonic acid excreted and of oxygen taken up in two of Pet- 

 tenkofer & Yoit's experiments which strikingly illustrate 

 this point. The numbers in the column headed " E" are 

 relative, and show how many grammes of oxygen appeared 

 in the excreted carbonic acid for every hundred grammes 

 taken up from the atmosphere. 



These experiments are included in the averages on p. 207. 



