The question that now confronted the observers was whether the stimulation of nuclear metabolism was an _inherent_ property of amino-acids. If so, “_substituted_ amino-acids might be expected to exert a similar influence.” But, if on the contrary, it was due not to the amino-acids as such but “either to the cellular work of their katabolism or to the intermediary products of their breakdown, a substituted amino-acid which does not follow the normal path of amino-acid catabolism would in all probability be devoid of the power of stimulation.” To this end, they selected _sarcosine_ or _methyl-glycocoll_ to elucidate the point at issue; this, inasmuch as it has been found to pass through the organism for the most part unchanged. The result justified their inference, for _no_ perceptible influence on uric acid excretion was noted. Hence, on the basis of this experiment, they inferred that the stimulation of uric acid metabolism was not an _inherent_ property of _amino-acids_; in other words, that if an amino-acid when ingested does not undergo disruptive katabolism, it is without effect on uric acid excretion. Now _deaminisation_ is the first stage in the katabolism of _amino-acids_, yielding as products _ammonia_ and _a-ketonic_ or _hydroxy acids_. The ammonia thus formed normally undergoes conversion into _urea_ and is excreted as such. In order to ascertain whether the _ammonia_ stimulated uric acid excretion, _ammonium chloride_ was administered, but no rise in the uric acid output above the normal level ensued. Also, the ingestion of _urea_ seemed to entail no appreciable increase in the uric acid elimination; in other words, these katabolic products of the _nitrogenous_ moiety of the amino-acids are without effect. As to the _non-nitrogenous_ intermediary products of the katabolism of amino-acids, _i.e._, the _a-ketonic_ or _hydroxy acids_, it was impossible to investigate the influence of these on the endogenous uric acid elimination.[14] Lusk also has brought forward evidence that in the presence of amino-acids cellular activities are intensified markedly. According to Taylor and Rose, too, not only _nuclear katabolism_, but also _nuclear anabolism_, may be accelerated by the presence of large amounts of amino-acids. Lewis and his collaborators consider that the results of their researches militate against Mares’ hypothesis, viz., that the origin of the increased amounts of endogenous uric acid that follow the intake of purin-free protein stuffs is referable to _intensified activity of the digestive glands_. _They hold that “it can be accounted for equally well as the result of a general stimulation of all cellular metabolism by the products of digestion of proteins the amino-acids.”_