2. Неличные формы глагола. Gerund.

1. Найдите в тексте The stages of digestion предложения в одном из времен группы Continuous Active. Укажите сказуемое.

2. Укажите грамматическую форму глаголов, оканчивающихся на

- ing в следующих предложениях:

a) The alimentary canal begins above with the cavity of the mouth traversing in its course the length of the thoracic and abdominal cavities.

b) The chemical action taking place in the mouth is accomplished by means of the saliva.

c) The teeth crush and break the food into fragments of proper size for swallowing.

d) The saliva assists in mastication in several ways: by dissolving some of the readily soluble food components; by partly digesting some of starch; by softening the mass of food; by covering the bolus with mucus.

e) In man the act of mastication has more significance than the mere grinding of food preparatory to swallowing.

f) While we are chewing the food, it is moving about in the mouth so that the taste buds are being stimulated and odors are being released to stimulate the olfactory epithelium.

Summary

6.1 Vitamins

Vitamins are organic chemical substances, widely distributed in natural foodstuffs, that are essential to normal metabolic functioning of human beings and lower animals. Only very small amounts are needed, but lack of the necessary amount, however small, results in a vitamin-deficiency disease (avitaminosis). Among the classical examples of such diseases are rickets, scurvy, beriberi, and pellagra.

The word vitamin was invented in 1911 by a Polish chemist, Casimir Funk, who was trying to ex­tract from rice hulls a chemical substance that would cure beri-­ beri. He thought he had found an amine chemical vital to life. He hadn't, but his theory was correct: lack of certain chemical substances caused disease.

The chemical structure of many vitamins is known. They are used to enrich foods, notably flour, from which natural vitamins are re­moved in the manufacture. Vitamins in the body enter into the complicated enzyme reactions by which food is digested, absorbed, and assimilated. When different vitamins were first discovered, it was common practice to name them by letters of the alphabet. So many have now been found that it is more practical to give them chemical names. Thus vitamin B1 is now called thiamine; vitamin C - ascorbic acid.

Vitamins are distinguished as fat-soluble — notably vitamins A, D and К — and water-soluble — most of the others. Some are heat-labile, destroyed by cooking, notably vitamin C; most are heat-stable.

Are vitamin pills necessary? Generally, no. A good mixed diet of common foods supplies a human being with all the vitamins he needs. Adding vitamin pills or concentrates to a good mixed diet will not increase resistance to disease. Multiple vitamins plus minerals in inexpensive tablets or capsules, taken once a day, represent a convenient way to fortify one's diet. Fortunately, moderate overdoses of vitamins do no harm. Vitamin supplements are sometimes clearly necessary. They are needed whenever the dietary intake of vitamins is inadequate. This condition frequently occurs in the presence of severe illnesses, after surgical operations, on low-calorie reducing diets, and during pregnancy. Vitamin needs differ with age. Thus vitamin D is much more essential to infants and growing children than to adults.

Vitamins in the diet: Practically speaking, only a few of the many vitamins have to be seriously considered in formulating diets. These important vitamins are A, C, D, and the vitamin В complex.

Vitamin A, once called the "anti-infective vitamin," helps to preserve the integrity of the skin and mucous membranes and other epithelial tissue, making them more resistant to infection. It aids growth and tooth formation. Vitamin A is found in fish oils (e.g. cod-liver oil), liver, milk, eggs and many green and yellow vegetables, where it exists as carotene.

Vitamin В complex includes a large number of water-soluble vitamins, including thiamine, riboflavin, niacin, pyridoxine, biotin, pantothenic acid, inositol, folic acid, and vitamin B12. They are essential for utilization of carbohydrates, some amino acids, normal appetite, and function of the digestive tract. Vitamin B12, derived from liver, increases the formation of red blood cells and useful in treating anemia. Best sources of vitamin B complex are pork, whole grain, dried peas and beans, milk, salmon, eggs and liver.

Vitamin C, or ascorbic acid, is a delicate vitamin, not well stored in the body and easily destroyed by heat. It supplies a kind of cementing substance that binds cells together in the blood vessels, teeth, bones, and other tissues. Lack of it causes the capillary blood vessels to break rather easily, producing such symptoms as bleeding gums, bleeding under the skin, poor teeth. These are some of the symptoms of scurvy, a disease both prevented and cured by administration of vitamin C. The best sources of vitamin С are citrus fruits—grapefruit, oranges, lemons, limes—and to­matoes.

Vitamin D, the "sunshine vitamin," is essential to the utilization of calcium and phosphorus, especially in proper bone and tooth formation. Infants and growing children particularly need this vitamin. Lack of it induces rickets and other bone disorders. Adults have little need of vitamin D supplements. When exposed to sunlight, the human body manufactures its own vitamin D. The ultraviolet rays of the sun turn sterols, fatty substances found in the human skin, into vitamin D. Fish-liver oils are excellent sources of vitamin D; so are liver, butter, and eggs.

Vitamin K, or the coagulation vitamin, is needed by the human liver to produce prothrombin, essential to normal blood clotting. It is particularly necessary, and may be given, by injection, to newborn infants to prevent bleeding. Vitamin К is derived from alfalfa, fish meal, and hempseed oil.

Did you know?

The longest time anyone has

ever lived without food or water