oxygen and the hydrogen may be removed from the ammonium carbonate, the simplest answer will be that the hydrogen is removed by oxidation and the oxygen by reduction. Experiment has confirmed my expectations. If an aqueous solution of ammonium carbonate is submitted to electrolysis, reversing the current and employing platinum or graphite electrodes, small quantities of urea are formed, which may be isolated and identified as such with certainty. By the evolution of hydrogen and oxygen, alternately at short intervals, the hydrogen is removed by oxygen, and the oxygen is eliminated by hydrogen, and urea remains.
Since both oxidation and reduction are continually taking place in the body, the solution of the question how urea is formed is given, viz., from the ammonium carbonate which is first formed it is produced by further oxidation and reduction.
Here we have urea produced without the body, under conditions which may be assumed to exist within; above all, the temperatures were such as are noted in animals. For this reason this synthesis is particularly adapted to show an acceptable process of the formation of urea in the organism. The question, by what means the organism effects the oxidations and reductions, whether electrolytically or chemically, of course, remains unanswered, but this will also be solved as soon as the processes taking place in the animal system are better known.
This synthesis also distinctly shows what developments physiology is to expect from pure chemistry. The experiments made on animals, by which the conversion of ammonia into urea in the organism was first established, did not teach a single fact which would have indicated that this conversion is the result of two directly opposite processes. This supposition was arrived at, independently of the experiments with animals, by purely chemical considerations, and it was simply necessary to furnish the experimental evidence of their correctness. In this, as in all similar cases, the physiological experiment will disclose the occurrence of synthesis and decompositions; and it will be the province of pure chemistry to discover the ways and means by which the organism produces the results. Both physiological and chemical experiments will have to be jointly and yet independently made, if the chemistry of the living organism is to be established.
Though we must confess that our knowledge of the chemical processes in the animal body is still very incomplete, we must recognize that the investigations made in this direction have given us much information. Though the substances which react on each other are known in the fewest cases, we have obtained hints regarding the manner in which they react. It has been shown why we are obliged to assume that oxidation takes place. We are also acquainted with processes which indicate reduction, others in which decomposition takes place with the assimilation of water, or synthesis with the elimination