The Elements of Agriculture. George Edwin Waring

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СКАЧАТЬ animal is formed from the first class of proximates?

      From the second?

      Which contains the largest portions of inorganic matter, plants or animals?

      Must animals have a variety of food, and why?

      Animals are composed (like plants) of organic and inorganic matter, and every thing necessary to build them up exists in plants. It seems to be the office of the vegetable world to prepare the gases in the atmosphere, and the minerals in the earth for the uses of animal life, and to effect this plants put these gases and minerals together in the form of the various proximates (or compound substances) which we have just described.

      In animals the compounds containing no nitrogen comprise the fatty substances, parts of the blood, etc., while the protein compound, or those which do contain nitrogen, form the muscle, a part of the bones, the hair, and other portions of the animal.

      Animals contain a larger proportion of inorganic matter than plants do. Bones contain a large quantity of phosphate of lime, and we find other inorganic materials performing important offices in the system.

      In order that animals may be perfectly developed, they must of course receive as food all of the materials required to form their bodies. They cannot live if fed entirely on one ingredient. Thus, if starch alone be eaten by the animal, he might become fat, but his strength would soon fail, because his food contains nothing to keep up the vigor of his muscles. If on the contrary the food of an animal consisted entirely of gluten, he might be very strong from a superior development of muscle, but would not be fat. Hence we see that in order to keep up the proper proportion of both fat and muscle in our animals (or in ourselves), the food must be such as contains a proper proportion of the two kinds of proximates.

      Why is grain good for food?

      On what does the value of flour depend?

      Is there any relation between the ashy part of plants and those of animals?

      How may we account for unhealthy bones and teeth?

      It is for this reason that grain, such as wheat for instance, is so good for food. It contains both classes of proximates, and furnishes material for the formation of both fat and muscle. The value of flour depends very much on the manner in which it is manufactured. This will be soon explained.

      What is a probable cause of consumption?

      What is an important use of the first class of proximates?

      What may lungs be called?

      Explain the production of heat during decomposition.

      Why is the heat produced by decay not perceptible?

      Apart from the relations between the proximate principles of plants, and those of animals, there exists an important relation between their ashy or inorganic parts; and, food in order to satisfy the demands of animal life, must contain the mineral matter required for the purposes of that life. Take bones for instance. If phosphate of lime is not always supplied in sufficient quantities by food, animals are prevented from the formation of healthy bones. This is particularly to be noticed in teeth. Where food is deficient of phosphate of lime, we see poor teeth as a result. Some physicians have supposed that one of the causes of consumption is the deficiency of phosphate of lime in food.

      Why is the heat produced by combustion apparent?

      Explain the production of heat in the lungs of animals?

      Why does exercise augment the animal heat?

      Under what circumstances is the animal's own fat used in the production of heat?

      The first class of proximates (starch, sugar, gum, etc.), perform an important office in the animal economy aside from their use in making fat. They constitute the fuel which supplies the animal's fire, and gives him his heat. The lungs of men and other animals may be called delicate stoves, which supply the whole body with heat. But let us explain this matter more fully. If wood, starch, gum, or sugar, be burned in a stove, they produce heat. These substances consist, as will be recollected, of carbon, hydrogen, and oxygen, and when they are destroyed in any way (provided they be exposed to the atmosphere), the hydrogen and oxygen unite and form water, and the carbon unites with the oxygen of the air and forms carbonic acid, as was explained in a preceding chapter. This process is always accompanied by the liberation of heat, and the intensity of this heat depends on the time occupied in its production. In the case of decay, the chemical changes take place so slowly that the heat, being conducted away as soon as formed, is not perceptible to our senses. In combustion (or burning) the same changes take place with much greater rapidity, and the same amount of heat being concentrated, or brought out in a far shorter time, it becomes intense, and therefore apparent. In the lungs of animals the same law holds true. The blood contains matters belonging to this carbonaceous class, and they undergo in the lungs the changes which have been described under the head of combustion and decay. Their hydrogen and oxygen unite, and form the moisture of the breath, while their carbon is combined with the oxygen of the air drawn into the lungs, and is thrown out as carbonic acid. The same consequence—heat—results in this, as in the other cases, and this heat is produced with sufficient rapidity for the animal necessities. When an animal exercises violently, his blood circulates with increased rapidity, thus carrying carbon more rapidly to the lungs. The breath also becomes quicker, thus supplying increased quantities of oxygen. In this way the decomposition becomes more rapid, and the animal is heated in proportion.

      Thus we see that food has another function besides that of forming animal matter, namely to supply heat. When the food does not contain a sufficient quantity of starch, sugar, etc., to answer the demands of the system the animal's own fat is carried to the lungs, and there used in the production of heat. This important fact will be referred to again.

      CHAPTER VII

LOCATION OF THE PROXIMATES AND VARIATIONS IN THE ASHES OF PLANTS

      Of what proximate are plants chiefly composed?

      What is the principal constituent of the potato root?

      Of the carrot and turnip?

      What part of the plant contains usually the most nutriment?

      Let us now examine plants with a view to learning the location of the various plants.

      The stem or trunk of the plant or tree consists almost entirely of woody fibre; this also forms a large portion of the other parts except the seeds, and, in some instances, the roots. The roots of the potato contain large quantities of starch. Other roots such as the carrot and turnip contain pectic acid,10 a nutritious substance resembling starch.

      It is in the seed however that the more nutritive portions of most plants exist, and here they maintain certain relative positions which it is well to understand, and which can be best explained by reference to the following figures, as described by Prof. Johnston:—

      Fig. 1.

      "Thus a shows the position of the oil in the outer part of the seed—it exists in minute drops, inclosed in six-sided cells, which consists chiefly of gluten; b, the position and comparative quantity of the starch, which in the heart of the seed is mixed with only a small proportion of gluten; c, the germ or СКАЧАТЬ