Probably both carbon atoms are able to enter into the formation of glucose. Present in most proteins; in large amount in gelatin; absent in milk proteins and in gliadin of wheat.

It has been noted that when benzoic acid is administered to an animal it forms a synthetic compound with glycocoll within the organism which is eliminated in the urine as hip-puric acid.

1 Ringer: "Journal of Biological Chemistry," 1913, xiv, 43.

C6H5.COOH + CH2.NH2.COOH = C6H5CO.NHCH2.COOH + H2O.

Hippuric acid is found in the urine of horses and cattle in the food of which materials convertible into benzoates are found. It is eliminated almost as soon as it is formed, for Lewis1 found after administering hippuric acid to a man that 82 per cent, could be recovered in the urine within three hours.

Lewinski2 found that when 10 or 20 grams of benzoic acid were administered to a man in the form of sodium benzoate the entire quantity of benzoic acid was combined and eliminated in the form of hippuric acid. Only when the power to form glycocoll was exceeded was there an elimination of benzoic acid. Thus, after giving 50 grams of benzoic acid, 62.3 grams of hippuric acid containing 42.3 grams of combined benzoic acid were eliminated, together with 8.2 grams of uncombined acid.

The following data are taken from Lewinski's experiments upon the same individual when partaking of low and of high protein diets. The figures are for twenty-four hours:

When there were 9 grams of total nitrogen eliminated, 3.15 grams or 35 per cent, appeared in the form of glycocoll. When 29 grams of total nitrogen, only 4.87 grams of nitrogen appeared in the form of glycocoll. In other words, an increase of 20 grams of nitrogen in the urine was accompanied by an increase of 1.72 grams of glycocoll nitrogen, which is only 8.5 per cent, of the increase in protein metabolism instead of 35 per cent.

1 Lewis: "Journal of Biological Chemistry," 1914, xviii, 225. 2 Lewinski: "Archiv fur ex. Path, und Pharm.," 1908, lviii, 397. See also Dakin: "Journal of Biological Chemistry," 1909-10, vii, 103.

Magnus-Levy1 found that 25 to 27 per cent, of the total urinary nitrogen of rabbits fed with cream and of a goat fed with hay is excreted in the form of hippuric acid when ben-zoate of soda is administered with the food. He calculated that only 4 per cent, of this could have been derived from glycocoll preformed in the protein metabolized, but that 20 per cent, could have originated from leucin did this pass through a glycocoll stage.

It has already been stated that the individual amino-acids lose their nitrogen as the first step in their metabolism. Only by the union of its nitrogen atom with benzoic acid is glycocoll spared this fate. One might believe that other amino-acids might unite with benzoic acid in a similar fashion, and then be converted into hippuric acid by oxidation of the rest of their carbon chains. To test this hypothesis, Magnus-Levy2 administered subcutaneously benzoylated compounds of alanin, valin, leucin, phenylalanin, aspartic acid, glutamic acid, ornithin, and serin. He found that these compounds were not changed into hippuric acid in the organism, but were eliminated unchanged in the urine.

These experiments were a further demonstration that in the breaking down of amino-acids deamination is the first step, and they leave no conclusion open other than that glycocoll arises by a synthetic process.

The nature of the process is still a riddle. The great elimination of glycocoll in hippuric acid has been repeatedly observed by Wiechowski3 and by Ringer,4 the latter finding that 38 per cent, of the total nitrogen may be eliminated as hippuric-acid nitrogen in the fasting goat. Parker and Lusk5 suggested the synthetic origin of glycocoll, but reported that carbohydrates had no influence on the excretion of hippuric acid. Abderhalden and Strauss6 gave a pig which was nourished on bran and potatoes 12 grams of sodium benzoate daily, and during certain periods added glycocoll, alanin, and ammonium carbonate. The results were as follows:

1 Magnus-Levy: "Munchener medizinische Wochenschrift," 1905, lii, 2168. 2Magnus-Levy: "Biochemische Zeitschrift," 1907, vi, 541. 3 Wiechowski: "Hofmeister's Beitrage," 1906, vii, 204. 4 Ringer: "Journal of Biological Chemistry," 1911, x, 327.

5 Parker and Lusk: "Amer. Jour, of Physiology," 1899-1900, iii, 472.

6 Abderhalden and Strauss: "Zeitschrift fur physiologische Chemie," 1914, xci, 81.

From this it appears that glycocoll when given with the benzoate is far from being completely removed in the urine, and that neither alanin which yields ammonia on deamination nor ammonium carbonate itself have any effect whatever on the elimination of glycocoll.

McCollum and Hoagland1 have reported some remarkable experiments. A pig, weighing 46.7 kilograms, was brought into a condition of minimal nitrogen metabolism by giving a diet of starch containing 75 calories for each kilogram of body weight. The diet was then continued and increasing amounts of benzoic acid were added. Finally, hydrochloric acid and benzoic acid were given together. The results of the urinary analyses are here reproduced:

* This includes hippuric acid.

1 McCollum and Hoagland: "Journal of Biological Chemistry," 1913-14, xvi, 299. See also Lewis: Ibid., 1914, xviii, 225.

It is evident from this that when the protein metabolism is reduced to a minimal level by carbohydrate ingestion (see p. 273) the addition of benzoic acid does not affect the creatinin output, scarcely affects the total nitrogen elimination, but may reduce the total elimination of urea nitrogen from 56 per cent, of the total nitrogen output to 19 per cent, of the total. This difference, or 37 per cent., of the total nitrogen which is ordinarily converted into urea is under these circumstances eliminated as glycocoll. It is of great significance that this is accomplished without materially changing the amount of protein metabolism (see p. 286). Giving hydrochloric acid with benzoic acid greatly increases ammonia formation, but scarcely influences the other urinary constituents (see p. 219). The urea elimination remains at its former minimal level.