This section is from the book "The Human Body: An Elementary Text-Book Of Anatomy, Physiology, And Hygiene", by H. Newell Martin. Also available from Amazon: The Human Body.
All meats, whether derived from beast, bird, or fish, are highly valuable foods. They contain abundant albumen, more or less fat, and, when cooked, their connective tissue is in great part turned into gelatin. Pork is the least easily digested form of fresh meat, and contains a larger percentage of fat than most This fat, which, by its oxidation liberates much heat, makes it a good food in cold weather for persons with a good digestion. Pigs are especially liable to a parasite, called trichina, which lives in their muscles, and may be transferred thence to man, sometimes causing death. Hence pork should always be thoroughly cooked. Salted meats of all kinds are less digestible and less nutritious than fresh. Milk contains an albuminous substance (casein), also fats (butter), and a sugar, known as sugar of milk, in addition to useful mineral alimentary principles. It will support life longer than any other single food. Cheese consists essentially of the casein of milk: it is a very nutritive albuminous food. Eggs contain albumens and fats, and have a high nutritive value: they are more easily digested when cooked soft than hard. Wheat contains more than a tenth of its weight of proteids, more than half its weight of starch, some sugar, and a little fat. The albumen of wheat flour is mainly gluten, which when moistened with water forms a tenacious mass, and this it is to which wheaten bread owes its superiority. When the dough is made, yeast is added to it and causes fermentation by which, among other things, carbon dioxide gas is produced.* This gas, imprisoned in the tenacious dough and expanded by heat during baking, forms cavities in it, and causes the dough to "rise" and make "light bread," which is not only more pleasant to eat but more easily digested than heavy. Some grains contain a larger percentage of starch, but none have so much gluten as wheat; when bread is made from them the carbon dioxide gas escapes so readily from the less tenacious dough that it does not expand the mass properly. Corn contains less albumen, more starch, and more fat than wheat. Rice is poor in albumen but very rich in starch. Peas and beans are rich in albumen and contain about half their weight of starch. Potatoes are not very nourishing because they contain a great deal of water and only about one pound of albumen and fifteen pounds of starch in every hundred pounds of potatoes. Other fresh vegetables, as carrots, turnips, and cabbages, are valuable mainly for the salts they contain; their weight is chiefly due to water, and they contain but little starch, albumens, or fats. Fruits, like most fresh vegetables, are mainly valuable for their saline constituents, the other foodstuffs in them being only present in small proportion. Some kind of fresh vegetable is, however, a necessary article of diet, as shown by the scurvy which used to prevail among sailors before fresh vegetables or lime-juice were supplied to them.
Give illustrations of the strength of the desire for salt. Why are meats valuable foods? How does pork differ from other fresh meats? Why is pork not a good form of food for summer?
Why should pork be well cooked ? How do salted meats differ in value as articles of diet from fresh? What foodstuffs exist in milk? What one food will support life longest? What is the chief alimentary principle in cheese? What is the nutritive value of cheese? What makes the value of eggs as foods? Are they more easily digested soft or hard boiled? What foodstuffs exist in wheat? Why is wheaten bread lighter than that made from other grains?
* The small amount of alcohol generated in the fermentation or rising of bread readily passes off in the heat of the oven. There is no alcohol in well baked bread.