554 METABOLISM, NUTRITION AND DIETETICS 



Phosphorus Poisoning and Migration of Fat. 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 changes in the 

 organs, 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 loaded with 

 fat. 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 much more than 

 the normal amount. It was assumed that 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 in the adipose tissue is greatly reduced. It was there- 

 fore concluded that the source of the fat could only have been the 

 broken-down protein. Since the nitrogen excretion was increased, while 

 the carbon excretion was diminished, it was supposed that a residue 

 rich in carbon must have been split off from the proteins, and, remaining 

 unburnt in the body, must have been converted into fat. Experiments 

 of this kind are open to criticism on several grounds, but especially on 

 this : that unless the fat-content of the whole body before the adminis- 

 tration of the poison is known, it is impossible to be sure that the fat 

 in a particular tissue has not been increased simply by the transportation 

 of fat from some other tissue. It has been conclusively shown that 

 migration of preformed fat does occur, and on an extensive scale, in 

 phosphorus poisoning. For example, a dog was fed for a time with 

 sheep's tallow, and fat was laid down in its adipose tissue with the 

 physical and chemical characters, not of dog's, but of sheep's fat. The 

 animal was then poisoned with phosphorus, and the fat which accumu- 

 lated in the liver examined. It also resembled sheep's fat, as it should 

 have done had it migrated from the adipose tissue, and not dog's fat, 

 as it might have been expected to do had it been formed in the hepatic 

 cells from protein . The ease with which connective -tissue fat i.e., food 

 fat migrates to the liver suggests, with other facts, that the liver has a 

 special relation to the transformation of this fat into the fat of the organs. 

 This ' organized ' intracellular fat differs in various ways from the fats 

 of adipose tissue. Its ' iodine value ' (p. 4) is higher (Leathes), and a 

 large proportion of it consists of phosphatide lipoids (p. 562). 



The most convincing evidence that fat is not produced in increased 

 amount under the influence of phosphorus has been obtained by deter- 

 mining by actual analysis the total fat in animals, then poisoning 

 similar animals with phosphorus and again estimating the total fat. 

 Far from being increased, the fat may even be decreased in the poisoned 

 animals (Taylor, etc.). There is no ground, then, for the assumption 

 that phosphorus and other substances, like arsenic, antimony, etc., which 

 bring about so-called ' fatty degeneration ' of the organs, act by causing 

 or accelerating the transformation of protein into fat. Yet there is good 

 evidence that they do accelerate the decomposition of protein, or at 

 least interfere with its normal metabolism, for after phosphorus poison- 

 ing amino-acids (leucin, tyrosin, glycin) appear in the urine. The 

 observations of Lusk and his pupils indicate that phosphorus does not 

 directly increase the amount of protein broken down, but does so 

 indirectly, by favouring the conversion of the carbohydrate-like radicle 

 of the protein molecule into leucin, tyrosin, and perhaps fat, and 

 thereby necessitating an increased consumption of protein. 



A celebrated experiment, performed nearly forty years ago, was long 



