Gelatine
This is what Liebig says in his Letters on Chemistry:-"It had been long observed that soup made by boiling meat, when concentrated to a certain point, gelatinises or forms a jelly; and people without any sufficient reason adopted the opinion that the substance (gelatine) was the most important, indeed the chief, constituent of good soup. Thus it came to pass by degrees that people took to the gelatinising matter for the true soup; and as manufacturers found that the best meat did not yield the finest jelly tablets, but that tendons, feet, cartilage, bones, ivory and hartshorn yielded the most beautiful and transparent jelly tablets, which were cheaply obtained and sold at a high price, ignorance and the love of gain exchanged the valuable constituents of flesh for gelatine which was only to be distinguished from common joiners' glue by its high price. It has now been proved by the most convincing experiments, that gelatine, which by itself is tasteless and when eaten excites nausea, possesses no nutritive value; that it is not capable of supporting the vital process; and that when added to the usual diet it diminishes the nutritive value of the food. Its use Geneva has been shown to be hurtful rather than beneficial. We now know that the active ingredients of soup are found ready formed in the aqueous infusion of flesh, and are not products of the culinary operations. The gelatine of soup is formed by long boiling of the flesh from the cellular membrane of the muscular tissue. Since these things have been ascertained, the use of gelatine as a nutritive and invigorating substance has been entirely given up; and it only retains a place in the domain of unscientific cookery. The gelatinous soups made in China from the air-bladder of fishes, and in England from the flesh of turtle, are a fertile source of disturbance in the digestive process." Other experiments prove that though gelatine by itself may have no nutritive value, it serves a good purpose which is not yet understood. There is no gelatine in the blood of animals; there is no gelatine in the milk on which an infant thrives. But there is a curious experiment which has yet to be worked out, and which shows that gelatine has its use in food. Bischoff and Voit took a dog weighing 80 lbs.-and that is a good-sized dog. They fed it on very nearly 18 ounces of meat a day, and at the end of four days the dog lost a pound weight. They then fed it for three days on the same quantity of meat, to which they added daily seven ounces of gelatine. At the end of the time, not merely had the dog lost nothing in weight, but also it gained four-and-a-half-ounces.