86 THE AMINO ACIDS 



reverse takes place, for a part of the tissue proteins is 

 converted into circulating proteins, which are metabo- 

 lized, and in this case the flesh of the body decreases." 

 (Hammarsten.) 



PFLUGER 



In 1893 Pfliiger severely criticised the theory of 

 Voit and offered another in its place. In its essence 

 the theory of Pfliiger rests upon the hypothesis that 

 food protein must become living protoplasm before 

 it can be utilized for the needs of the body. In accord- 

 ance with this idea he assumed that food protein is 

 catabolized with great difficulty whereas living proto- 

 plasm is in a state of continual unstable equilibrium 

 leading to any easy oxidation or decomposition of its 

 protein. Pfliiger's theory rests upon experiments 

 carried through by his pupil Schondorff. It was shown 

 by Schondorff that when the blood from a starving 

 dog was passed through the hind limbs and liver of 

 a well-fed animal the urea of this blood was increased. 

 On the other hand, no increase of urea could be ob- 

 tained when blood, whether of starved or well-fed 

 dogs, was passed through the hind limbs and liver of 

 a starved dog. From the results Pfliiger argued that 

 the determining factor in protein catabolism is the 

 state of nutrition in the tissue cells and not the cir- 

 culating protein. 



Although in general Pfliiger appeared to disprove 

 many of the points in Voit's theory, one positive evi- 

 dence stands out clearly in favor of Voit's theory, and 



