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and the resistance to depressing external influences diminished. When taken through a long period of time, alcohol impairs digestion, produces gastric catarrh, disorders the secreting power of the hepatic cells. It also diminishes the muscular power and destroys the structure and composition of the cells of the brain and spinal cord. The connective tissue of the body increases in amount, and subsequently contracting, gives rise to sclerosis.
A Proper Combination of different alimentary principles is essential for healthy nutrition, no one class being capable of maintaining life for any definite length of time.
The albuminous food in excess promotes the arthritic diathesis, manifesting itself as gout, gravel, etc.
The oleaginous food in excess gives rise to the bilious diathesis, while a deficiency of it promotes the scrofulous.
The farinaceous food, when long continued in excess, favors the rheumatic diathesis by the development of lactic acid.
The Alimentary Principles are not introduced into the body as such, but are combined in proper proportions to form compound substances, termed foods, e..., bread, milk, eggs, meat, etc., the nutritive value of each depending upon the extent to which these principles exist.
The Amount of Food required in 24 hours is estimated from the total quantity of carbon and nitrogen excreted from the body in 24 hours; these two elements representing the waste or destruction of the carbonaceous and nitrogenized compounds. It has been determined by experimentation that about 4600 grains of carbon and about 300 grains of nitrogen are eliminated from the body daily, the ratio being about 15 to 1. That the body may be kept in its normal condition, a proper proportion of carbonaceous (bread) to nitrogenized (meat) food should be observed in the diet.
The method of determining the proper amounts of both kinds of food is as follows:
1000 grains of bread (2 oz). contain 300 grs. C. and 10 grs. N. To obtain the requisite amount of nitrogen from bread, 30,000 grains, or about 4 lbs., containing 900 grains of carbon and 300 of nitrogen, would have to be consumed. Under such a diet there would be a large excess of carbon, which would be undesirable. On a meat diet the reverse obtains :
1000 grains of meat (2 oz.) contain 100 grs. C. and 30 grs. N. To obtain the requisite amounts of carbon from meat, 45,000 grains, or about 672 lbs., containing 4500 grains of carbon and 1350 grains of nitrogen, would have to be consumed. Under such circumstances there would arise an excess of nitrogen in the system, which would be equally undesirable and injurious. By combining these two articles, however, in proper proportion, the requisite amounts of carbon and nitrogen can be obtained without any excess of either, e.g.:
2 lbs. of bread contain 4630 grs. C. and 154 grs. N.
The amount of carbon and nitrogen necessary to compensate for the loss to the system daily would be contained in the above amount of food. As about 372 oz. of oil or butter are consumed daily, the quantity of bread can be reduced to 19 oz. In the quantities of bread and meat above mentioned, there are 4.2 oz. albumin, 9.3 sugar and starch.
DIGESTION. Digestion is a physical and chemical process, by which the food introduced into the alimentary canal is liquefied and its nutritive principles transformed by the digestive fluids into new substances capable of being absorbed into the blood.
The Digestive Apparatus consists of the alimentary canal and its appendages, viz. : teeth, salivary, gastric, and intestinal glands, liver and pancreas.
Digestion may be divided into seven stages : prehension, mastication, insalivation, deglutition, gastric and intestinal digestion, and defecation.
Prehension, the act of conveying food into the mouth, is accomplished by the hands, lips, and teeth.
Mastication is the trituration of the food, and is accomplished by the teeth and lower jaw, under the influence of muscular contraction. When thoroughly divided, the food presents a greater surface for the solvent action of the digestive fluids, thus aiding the general process of digestion.
The Teeth are thirty-two in number, sixteen in each jaw, and divided into four incisors or cutting teeth, two canines, four bicuspids, and six molars or grinding teeth; each tooth consists of a crown covered by enamel, a neck, and a root surrounded by the crusta petrosa, and imbedded in the alveolar process; a section through a tooth shows that its substance is made of dentine, in the center of which is the pulp cavity, containing blood vessels and nerves.
The lower jaw is capable of making a downward and an upward, a lateral and an antero-posterior movement, dependent upon the construction of the temporo-maxillary articulation.
The jaw is depressed by the contraction of the digastric, genio-hyoid, mylo-hyoid, and platysma myoides muscles; elevated by the temporal, masseter, and internal pterygoid muscles; moved laterally by the alternate contraction of the external pterygoid muscles; moved anteriorly by the pterygoid and posteriorly by the united actions of the genio- hyoid, mylohyoid, and posterior fibers of the temporal muscle.
The food is kept between the teeth by the intrinsic and extrinsic muscles of the tongue from within, and the orbicularis oris and buccinator muscles from without.
The Movements of Mastication, though originating in an effort of the will and under its control, are, for the most part, of an automatic or reflex character, taking place through the medulla oblongata and induced by the presence of food within the mouth. The nerves and nerve centers involved in this mechanism are shown in the following table :
NERVOUS CIRCLE OF MASTICATION.
AFFERENT OR EXCITOR NERVES.
EFFERENT OR MOTOR NERVES
1. Lingual branch of 5th pair.
1. 3d branch of 5th pair.
The impressions made upon the terminal filaments of the sensory nerves are transmitted to the medulla; motor impulses are here generated which