326 PHYSIOLOGY CHAP. 



Lebedeff and I. Munk, and still more G. Eosenfeld (1899), suc- 

 cessfully performed this experiment, which others had attempted 

 with doubtful results. Lebedeff succeeded in making two dogs 

 which had previously fasted for some time store up linseed oil in 

 the one case, mutton fat in the other. In the same way I. Munk 

 found rape oil and mutton suet in the fat of dogs after feeding 

 them with these substances. In man, too, he succeeded in 

 showing that extraneous fatty acids could be stored up in the form 

 of neutral fats. Rosenfeld not merely noted in dogs an abundant 

 storing up of mutton fat and cocoa butter, but was able, even after 

 a month in which these fats had not been administered, to 

 demonstrate mutton fat almost in the pure state in the animal's 

 body. 



The greater part of the fat stored up as reserve material in 

 the body, with the exception of the little derived immediately 

 from the alimentary fats, may be referred to the carbohydrates 

 or the proteins. Liebig, on the strength of a number of observa- 

 tions, particularly that bees fed on honey only, in which there is 

 very little protein, produce large quantities of wax, proposed the 

 theory that the greater part of the fat stored up in the body is 

 derived from carbohydrates. On the other hand, many other 

 observations to hand show that fats may arise from cleavage of 

 the complex protein molecule, when the nitrogenous group gives 

 rise to formation of urea, and the non-nitrogenous group to the 

 formation of fatty acid. The so-called fatty degeneration of the 

 tissues, in which the cytoplasm is converted into fat granules, is 

 a sufficiently cogent proof of this theory. The " maceration " of 

 cheese due to Penicillium glaucum is known to consist in a process 

 in which calcium paracasein decomposes with formation of fats, 

 ammonia, and other nitrogenous substances, which are found in 

 macerated cheese. 



A more direct proof of the derivation of fat from protein was 

 adduced by Bauer (1878) from slow phosphorus poisoning, which 

 produces fatty degeneration of all the tissues in different degrees. 

 When a dog had lost the whole of its nitrogen and carbon by 

 fasting, he began to inoculate it subcutaneously with minute 

 doses of phosphorus dissolved in oil. After several consecutive 

 days, the daily amount of nitrogen excreted with the urine was 

 doubled, while the elimination of carbon and absorption of oxygen 

 were diminished by half. Phosphorus poisoning, therefore, doubled 

 the consumption of protein, while the non-nitrogenous groups of 

 the protein molecule were stored up as fat. In fact, the post- 

 mortem showed fatty degeneration of all the organs. Bauer found 

 424 per cent fat in the dry substance of muscle, 30 per cent in 

 dry liver, while normally the first contains only 16 '7 per cent, and 

 the second only 104 per cent fat. We may, therefore, conclude that 

 fat is formed from protein in phosphorus poisoning. 



