"RMCS: Snow critiques R. D. Thomson's paper, "On the relation between the constituents of the food and the systems of animals.""

(12 May 1846)

The paper was written and delivered by R. D. Thomson, M.D., Lecturer on Practical Chemistry in the University of Glascow; the Lancet sent a reporter, who after giving minutes and commentary, noted that he considered much of the paper very original, although most of the fellows of the Society with whom he spoke disagreed.

In the paper, Thomson gave "formulae for calculating the amount of nutritive and calorifient food, with a view to determine the laws of dieting." He believed that Dr. Prout's views, while still generally accepted, have been challenged by findings in investigations undertaken by Magendie and Liebig.

During the question and answer period,

"Dr. Snow said that he considered organic chemistry would have to be much further advanced than it is at present, before it would be safe to follow it, in giving directions on diet, instead of being guided by experience. It was true, that farinaceous food did not suit young infants, especially in large quantity; so far, experience coincided with Dr. Thomson's theory; but if we were to argue, from the chemical constitution of the milk, as to what ought to be the chemical constitution of the food to be adopted after weaning, it would have to be a sort of diet that we had never know given to children; they could not digest beans, and the only alternative would be, an exclusively animal diet. But the fact was, that the chemical constitution of milk was no criterion of what should be the food afterwards; there was the smallest possible difference in the chemical constitution of the milk, which was the earliest food of all the mammiferous class; but no sooner was this left off, than they betook themselves to the most different kinds of nutriment, some living on grass, and other exclusively on flesh. This was in accordance with the circumstance, that there was a great resemblance in organization in the early period of the development of animals, and that they took in their specific characters as they grew up. Dr. Thomson had spoken of the albumen and other nitrogenous constituents of food as the nutritive part, and of the farina as the caloric portion. He had indeed admitted that the former might assist in the function of respiration, but he had not admitted that starch might assist in nourishing the fibrinous tissues. It happened, however, that many animals living exclusively on coarse vegetable food, of which the nitrogenized elements formed but a small part, were amongst the strongest and most active of the animal kingdom, and possessed a lower temperature than did, in general, the carnivora, many of which were lazy and inactive in their habits. Taking all circumstances into consideration, the opnion of Dr. Prout must be the true one-that the saccharine elements of the food, as he called them, combined with the nitrogenous principles of the bile, and were thus capable of renewing the waste of the body, and that the vegetable feeders were not condemned to burn off the greater part of their food as fuel in the lungs."

Golding Bird seconded Snow's critique, but cited Liebig rather than Prout - "that distinguished philosopher . . . had proved, that with the exception simply of the fatty tissues, every structure in the body was supported, and its waste supplied, by the nitrogenized elements of food. . . ."

"Royal Medical and Chirurgical Society," Lancet 1 (1846): 602.