456 A MANUAL OF PHYSIOLOGY 



converted into fat. The proof of this statement is very 

 complete, but only an outline of it can be given here. 



In the experiments of Bauer, the amount of oxygen consumed and 

 of carbon dioxide and nitrogen excreted was determined in starving 

 dogs. Phosphorus, which, as is well known, causes extensive fatty 

 degeneration, was then administered in small doses for several days. 

 The excretion of nitrogen was doubled, the excretion of carbon 

 dioxide and the consumption of oxygen diminished to one-half. 

 When the animals died, in a few days, the organs were all found 

 fattily degenerated. In one case 42*4 per cent of the solids of the 

 muscles and 30 per cent, of the solids of the liver consisted of fat. 

 This is nearly three times the normal amount. The fat could not 

 have been simply transferred from the adipose tissue, since the dog 

 had been starved for twelve days before the phosphorus was given, 

 and died on the twentieth day of starvation. Now, after such a 

 period of hunger the amount of fat necessary to account for the 

 excess found in the organs does not exist in the adipose tissue. The 

 source of the fat could only have been the broken down proteid. 

 Since the nitrogen excretion was increased, while the carbon excre- 

 tion was diminished, a residue rich in carbon must have been split 

 off from the proteids and, remaining unburntin the body, must have 

 been converted into fat. The observations of Lusk and his pupils 

 indicate that phosphorus does not directly increase the amount of 

 proteid broken down, but does so indirectly, by favouring the con- 

 version of the carbo-hydrate-like radicle of the proteid molecule into 

 leucin, tyrosin, and fat, and therefore necessitating an increased con- 

 sumption of proteid. 



These experiments show that in abnormal circumstances fat may 

 arise from proteids. An absolute proof of its formation in this 

 manner, under strictly physiological conditions, although in a 

 humble form of animal life, is afforded by the experiments of 

 Hofmann on maggots allowed to develop from the egg on blood 

 containing a known amount of fat. The quantity of fat" in the eggs 

 was also known. After the maggots had grown, ten times as much 

 fat was found in them as had been contained in the blood and eggs 

 together. The trifling quantity of sugar in the blood was utterly 

 inadequate to account for the fat, which must have come from the 

 proteids of the blood. 



That in the higher animals also fat is formed from proteids under 

 normal conditions is, although not perhaps strictly proved, yet 

 extremely probable. A dog fed for a time on a liberal diet of lean 

 meat may go on excreting a quantity of nitrogen equal to that in the 

 food, while there is a deficiency in the carbon given off. Or if the 

 dog is not in nitrogenous equilibrium (p. 460), but putting on 

 nitrogen in the form of ' flesh,' the deficiency in the carbon given off 

 may be too great in proportion to the nitrogen deficit to warrant the 

 assumption that all the retained carbon has been put on in the form 

 of proteid. In either case, carbon in large amount can only come 

 from the pioteids of the food, and can only be stored up in the body 



