The Chemistry of Cookery

by W. Mattieu Williams

Lehmann’s summary of the experiments of Abernethy, Brunner, and Valentin (vol. ii. p. 391), gives the amount of hourly exudation, under ordinary circumstances, as 50·71 grammes of water, 0·25 of a gramme of carbon, and 0·92 of a gramme of nitrogen. This amounts to 21½ grammes of nitrogen per day in the insensible perspiration; three-quarters of an ounce avoirdupois, or as much nitrogen as is contained in one pound and a half of natural living muscle.

That the liquid perspiration contains compounds of nitrogen, and just such compounds as would result from the degradation of nitrogenous tissue, is unquestionable. As Lehmann says (vol. ii. p. 389), ‘the sweat very easily decomposes, and gives rise to the secondary formation of ammonia.’ Simon and Berzelius found salts of ammonia in the sweat: that the ammonia is combined both with hydrochloric acid and with organic acids: that it probably exists as carbonate of ammonia in alkaline sweat.

The existence of urea in sweat appears to be uncertain; some chemists assert its presence, others deny it. Favre and Schottin, for example, who have both studied the subject very carefully, are at direct variance. I suspect that both are right, as its presence or absence is variable, and appears to depend on the condition of the subject of the experiment.

Favre describes a special nitrogenous acid which he discovered in sweat, and names it hydrotic or sudoric acid. Its composition corresponds, according to his analysis, to the formula C₁₀H₈NO₁₃.

I have summarised these facts, as they show clearly enough that conclusions based on an examination of the quantity of nitrogen excreted by the kidneys alone (and such is the sole basis of the modern theories), are of little or no value in determining whether or not muscular work is accompanied with degradation of muscular tissue. The well known fact that the total quantity of excretory work done by the skin increases with muscular work, while that from the kidneys rather diminishes, indicates in the plainest possible manner that an examination of the skin secretion should be primary in connection with this question. To entirely neglect this in such a research is a scientific parallel to the histrionic feat of performing the tragedy of ‘Hamlet’ with the Prince of Denmark omitted.

Seeing that it has been entirely neglected, I am justified in expressing, very plainly and positively, my opinion of the worthlessness of all the modern research upon which the alleged refutation of Liebig’s theory of the destruction and renewal of living tissue in the performance of vital work is based, and my rejection of the modern alternative hypothesis concerning the manner in which food supplies the material demanded for muscular and mental work.

I may be accused of rashness and presumption in thus attempting to stem the overwhelming current of modern scientific progress. Such, however, is not the case. It is modern scientific fashion, rather than scientific progress, that I oppose. We have too much of this millinery spirit in the scientific world just now; too much eagerness to run after ‘the last thing out,’ and assume, with undue readiness, that the ‘latest researches’ are, of course, the best—especially where fashionable physicians are concerned.

Having summarised Liebig’s theory of the source of vital power, and its supposed refutation by modern experiments, I will now endeavour to state the alternative modern hypothesis, though not without difficulty, nor with satisfactory result, seeing that the recent theorists are vague and self-contradictory. All agree that vital power or liberated force is obtained at the expense of some kind of chemical action of a destructive or oxidising character, and is, therefore, theoretically analogous to the source of power in a steam-engine; but when they come to the practical question of the demand for working fuel or food, they abandon this analogy.

Pavy says (‘Treatise on Food and Dietetics,’ page 6): ‘In the liberation of actual force, a complete analogy may be traced between the animal system and a steam-engine. Both are media for the conversion of latent into actual force. In the animal system, combustible material is supplied under the form of the various kinds of food, and oxygen is taken in for the process of respiration. From the chemical energy due to the combination of these, force is liberated in an active state; and, besides manifesting itself as heat, and in other ways peculiar to the animal system, is capable of performing mechanical work.’ In another place (page 59 of same work), after describing Liebig’s view, Dr. Pavy says: ‘The facts which have been already adduced’ (those above described on the nitrogen eliminated by the kidneys), ‘suffice to refute this doctrine. Indeed, it may be considered as abundantly proved that food does not require to become organised tissue before it can be rendered available for force-production.’ On page 81 he says: ‘While nitrogenous matter may be regarded as forming the essential basis of structures possessing active or living properties, the non-nitrogenous principles may be looked upon as supplying the source of power. The one may be spoken of as holding the position of the instrument of action, while the other supplies the motive power. Nitrogenous alimentary matter may, it is true, by oxidation contribute to the generation of the moving force, but, as has been explained, in fulfilling this office there is evidence before us to show that it is split up into two distinct portions, one containing the nitrogen, which is eliminated as useless, and a residuary non-nitrogenous portion which is retained and utilised in force-production.’

The italics are mine, for reasons presently to be explained. Pavy’s work contains repetitions and further illustrations of this attribution of the origin of force to the non-nitrogenous elements of food.