It has been noted that in completely phlo-rhizinized dogs the actual D : N ratio is 3.65 : 1. How accurately may one calculate the theoretic origin of glucose from the present amount of information at hand? If the analysis of muscle tissue given by Osborne (see p. 77) be taken, one may estimate how much sugar may arise from the various fragments of the protein molecule.

Calculation Showing The Origin Of Glucose From Protein

* Amount not given.

Since 100 grams of the ox muscle contained 16.18 grams of nitrogen and from this same material 44.4 grams of glucose may be calculated to arise, one may deduce the equation, D : N = 44.4/16.18 = 2.75 :1. If the D : N ratio is 3.65, 59 gm. of glucose, or 14.6 gm. more than the quantity above estimated, are eliminated in the urine when 100 gm. of protein are destroyed. These 14.6 gm. represent an additional amount of glucose, whose origin is unexplained and which is equal to 24 per cent, of the total maximal production. Such sources of sugar might be cystin, which, if all the sulphur in protein were in that form, might at most yield 2 grams of glucose, serin whose solubility prevents accuracy of determination, and glycocoll formed synthetically.

Though the analytic methods are admittedly crude, yet they give some insight into the possibilities of transformation of a heterogeneous medley of amino-acids into a common substance, glucose, the carbohydrate of the organism.1

Leucin, tyrosin, and phenylalanin, on the other hand, yield β-oxybutyric acid, or the end-product characteristic of fat metabolism, whereas the final products of valin, lysin, histidin, and tryptophan are unknown.