184 ANTHROPOLOGY. 



stomach after having been mixed with the sahvary secretion. In the sto- 

 mach, the food is acted on by the gastric juice, and reduced to a pulpy mass 

 termed chyme. Passing out of the pyloric orifice, the chyme enters the 

 small intestines, and after having been mixed with the juices secreted by the 

 pancreas and liver, becomes converted into chyle, and a residuum. The 

 former is taken up by the lacteals, and ultimately poured into the descend- 

 ing current of venous blood-, the latter passes in the form of excrement. 

 Such are the general changes which take place, to be more fully described 

 hereafter. 



Such substances are alone adapted for purposes of nutrition as contain 

 water, and a greater or less amount of organicjnatters capable of mixing 

 with the fluids of the body. Certain nations, indeed, forced by custom or 

 by necessity, devour mineral matters, as the Otomacs and Guamos in Guinea, 

 who eat a clay, the inhabitants of New Caledonia, who mix a certain earth 

 with their food, and the Laplanders, who in time of scarcity consume the 

 bergmehl, tripoli, &;c. ; but these contain a small amount of organic matter, 

 being composed almost entirely of the shields of infusoria. A long con- 

 tinued use of these substances is, however, exceedingly pernicious. Proper 

 food must contain organic matter in a form capable of being assimilated by 

 the digestive organs, and must include all the elements of the body. For 

 this reason, starch and sugar cannot alone sustain life for a great length of 

 time, owing to the absence of the necessary nitrogen, sulphur, phosphorus, 

 and lime ; and some substances even which fulfil these conditions may be 

 incapable of supporting life. Thus, the fibrine of the blood contains most 

 of the necessary elements, yet a dog fed exclusively upon it soon dies. The 

 same applies to the gelatine from boiled cartilage and bones, tendons and 

 ligaments. A well regulated alternation in the character of food consumed 

 is imperatively required by the system. Thus the coagulated white of egg, 

 when mixed with other substances, is exceedingly nutritious, yet animals 

 cannot live upon it exclusively for any great length of time without danger 

 to life. The same principle holds good in respect of the exclusive use of 

 meat or of any other food. 



The organs of digestion consist of an uninterrupted alimentary canal 

 extending from the lips to the anus, and of numerous glandular bodies 

 placed along its track, and pouring into it their secretions. This canal is in 

 three portions, a superior, middle, and inferior, constituted by, first, the 

 mouth, pharynx, and oesophagus ; second, the stomach and small intestines ; 

 and third, the large intestine. The glandular organs are the salivary glands, 

 the pancreas, the liver, and the spleen. 



1. Organs of Mastication and Deglutition. 



1. The Mouth. The mouth, or cavum ori, is bounded anteriorly by the 

 lips, superiorly by the hard and soft palate, laterally by the cheeks, inferiorly 

 by the tongue and mucous membrane reflected from it to the gums ; pos- 

 teriorly it communicates with the pharynx ; this opening is named the 

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