Page:Popular Science Monthly Volume 1.djvu/424

410 to contain these soda-salts almost exclusively, while in the urine were found only the salts of potash. The salts of soda thus were altogether retained, as in the case where the salts were withheld.

It is not the functions of the nutritive salts that have been exaggerated hitherto, but rather the proportion in which they must enter into the food. They might be withheld for as many as forty days, for they are found in sufficient quantity in all substances which contain the other elements of nutrition. Haubner has stated that pigeons fed on grain, without lime, quickly die; but Voit has kept them on such food for a whole year. On food deprived of salts a pigeon can live for about thirty days.

When it is said that, without the nutritive salts, the residuum of meat, or any other kind of food, possesses no nutritive value whatsoever, the statement is true only in a certain sense, and as far as the duration of complete nutrition is concerned. Within a certain period of time, in the absence of the salts, the albuminates will cease to be assimilated, as also the fats and the hydrates of carbon. It is the salts that render the organic elements nutritive. The author hence concludes that none of these elements, whether organic or mineral, have any absolute nutritive value, and that they cannot be considered apart by themselves. They coöperate mutually in nutrition, and so are all equally indispensable to constitute proper food, such as may support life and strength. This is the most important datum of the numerous and varied physiological experiments made in Germany during the past few years, and it is a new discovery for us. Our physiologists and hygienists had no suspicion of such facts.

As we consume, with our food, considerably more of these salts than is needed to support the body, the question arises, Is this simply surplus, or are we benefited by it, as being a flavoring for the food? Much has been said about the extractive elements of meat, and it has been supposed that these elements form the true distinction between animal and vegetable food. According to this view they constitute the peculiar action of meat and of meat-extract. Here we must make a distinction between the nutritive element and the condiment.

The extractive elements of flesh-meat are the products of regressive change, and are not necessary for the constitution and formation of the organs; nor can they, when taken with food, add to the substance of those organs. The elements of this extract have been got in isolated forms, as creatine, sarkine, taurine, urea, uric acid, tyrosine, lactic acid, acetic acid, etc.; each organ has its own characteristic extractive principles, or its own products of decomposition, the conditions of this decomposition varying for the various organs.