A Study of the Nitrogen Minimum

The “continuing” metabolism of nitrogen in animals

“…Martin and Robison (1922) pointed out that the logarithm of the difference between the daily nitrogen excretion at the low level, designated as a, and the daily excretion in the interval between the two levels, a, i.e., log (a-x), plotted against time gives a straight line. The same relationship is demonstrable in the data of the experiment of Deuel, Sandiford, Sandiford, and Boothby (1928). This logarithmic relation indicates that the decomposition of the nitrogen represented by (a-x), which we shall term the continuing metabolism, resembles a first-order reaction.…”

“…The chief difficulty in the way of accepting this hypothesis is that feeding a protein deficient in sulphur does not change the composition of the proteins of the liver (Lee and Lewis, 1934), the organ in which protein storage most readily occurs (Seitz, 1906;Gautier and Thiers, 1928;Gautier, 1929Gautier, , 1931Gautier, , 1933Addis, 1935), nor in the muscles. At the same time the large changes in the urinary nitrogensulphur ratio with changes in the diet show that the composition of the labile nitrogen, which is the store of nitrogen supporting the continuing metabolism, does vary in its nitrogen-sulphur ratio (Wilson, 1925;Cathcart and Burnett, 1925-26;Deuel, Sandiford, Sandiford, and Boothby, 1928). Nevertheless, the continuing metabolism is proof that storage of nitrogen does occur, and the findings are conclusive that this nitrogen is not stored in the form of amino acids.…”