The call for oxygen by the tissues 



105 



diverted. The greatest care must be taken to insure that the blood 

 is collected at the pressure at which it normally is in the vein. 



We performed two series of experiments. The determinations 

 were made as a rule about noon ; in the first series the animals were 

 given a clear day without food having been fed the evening before 

 that, there being therefore about 42 hours from the time of the last 

 meal till that of the experiment. In the second series the animal, 

 a cat in every case, was fed the evening before the experiment, i.e. 

 about 18 hours previously. In neither case was much food found in 

 the intestines and therefore it is not surprising that the difference 

 in the metabolism of the abdominal viscera which drain into the 

 portal system was trifling. But the metabolism of the liver was 

 markedly higher in the case of the fed animals than in the case of 

 the unfed ones, as the following figures show : 



Animals fasting 



Animals fed 



In our discussion of the call for oxygen we have reviewed the 

 activity of many organs of the body, muscle, heart, kidney, secreting 

 glands and absorbing epithelium ; these organs are excited by the 

 most diverse forms of stimulus, electrical stimuli, hormones, drugs, 

 &c., and evince their activity by doing work of the most diverse 

 kinds ; in one respect only do they resemble one another, namely that 

 in no organ excited by any form of stimulus can it be shown that 

 positive work is done without the blood supply having to respond to 

 a call for oxygen. 



