MAlSrUAL OF OATTLE-FEEDIN"G. 87 



In tlie Biglit-half of^ tlie experimentj there was taken in- 

 to the system tliroiigli the hmgs 104.63 grms. of oxygen 

 more than was used during that time in oxidizing food 

 substances and body-fat, while in the day-half of the ex- 

 periment more oxygen was tluis used than was supplied 

 from without, the remainder (159.99 grms.) evidentlj be- 

 ing drawn from a supply previously laid up in the body. 



In the earlier experiments of both Pettenkofer and Yoit 

 and Henneberg, the storing up of oxygen took place 

 chiefly, as in this case, in the night, but further investiga- 

 tions showed that this was by no means always the case. 

 It would seem, from these expeiiments, as if the healthy 

 animal body were constantly eitlier storing up or giving 

 off oxygen, the two processes, as a rule, nearly balancing 

 each other in the course of twenty-four hours, while com- 

 plete equilibrium is seldom reached in tliat time. The 

 signifieance of this fact we shall consider later. 



Decompositions of the Nutrients in the Body. — 

 T1w> aTbunmiolds of the food and tissues are believed to 

 split up, by numerous intermediate steps, into urea and 

 fatJ^ In the herbivora there are also formed varying 

 quantities of hippurie aouL according to the fodder and 

 the species of animal, but the latter always represents a 

 far smaller part of the decomposed albuminoids than the 

 urea, and often disappears almost completely from the list 

 of the substances formed and excreted as the result of 

 tissue-change. 



The urea is rapidly taken up by the blood, separated 

 from it again in the kidneys, and excreted in the urine ; it 

 can and ought never to be stored up in the healthy organ- 

 ism. In the normal blood and in the tissues are found 

 only inconsiderable traces of it, although the total quati- 



* See the chtipter on the " Formation of Fat '* 



