TISSUE AND CIRCULATING PROTEINS. 851 



increased supply of proteins, it indicates that the decomposing power of 

 the cells for proteins has increased so that the same quantity of proteins 

 is metabolized as is supplied to the body. If the protein metabolism is 

 decreased by the simultaneous administration of other non-nitrogenous 

 foods (see below), a part of the circulating proteins may have time to 

 become fixed and organized by the tissues, arid in this way the mass of 

 the flesh of the body increases. During starvation or with a lack of pro- 

 teins in the food the reverse takes place, for a part of the tissue proteins 

 is converted into circulating proteins which are metabolized, and in this 

 case the flesh of the body decreases. 



VOIT'S theory has been criticised by several investigators and 

 especially by PFLUGER. PFLUGER'S belief, based on an investigation 

 made by one of his pupils, ScHONDORFF, 1 is that the extent of protein 

 destruction is not dependent upon the quantity of circulating proteins, 

 but upon the nutritive condition of the cells for the time being a view 

 which does not widely differ from VOIT if the author does not misunder- 

 stand PFLL'GER. VOIT 2 has, as is known, stated that the conditions for 

 the destruction of substances in the body exist in the cells, and also that 

 the circulating protein is first catabolized after having been taken up 

 by the cells from the fluids washing them. The point of VOIT'S theory 

 is that all proteins are not destroyed in the body with the same degree of 

 ease. The organized protein, which is fixed by the cells and has become 

 a part of them, is destroyed less readily than the protein taken up by the 

 cells from the nutritive fluid, which serves as material for the chemical con- 

 struction of the much more complicated organized proteins. This nutritive 

 protein, which circulates with the fluids before it is taken up by the cells, 

 and which can exist in store in the cells as well as in the fluids, agreeably 

 to VOIT'S view, has been called circulating protein or store protein by 

 him. It is clear that these names may lead to misunderstanding, and 

 therefore too much stress should not be put upon them. The most 

 essential part of VOIT'S theory is the supposition that the food protein 

 of the cells is more easily destroyed than the organized, real protoplasmic 

 protein, and this assertion can hardly, for the present, be considered as. 

 refuted or exactly proven. 



The investigations in recent years, especially those of FOLIN, which 

 show that the amount of certain nitrogenous urinary constituents, such 

 as creatinine, uric acid and the combinations containing neutral sulphur 

 are almost independent of the quantity of protein taken as food, while 

 the quantity of urea is determined by the protein partaken of, tend to 

 substantiate VOIT'S view that we must differentiate between the real 

 cell protein and the food protein. This has also led FOLIN to differen- 



1 Pfliiger, Pfliiger's Arch., 54; Schondorff, ibid., 54. 



2 Zeitschr. f . Biologic, 11. 



