184 ANTHROPOLOGY. 
stomach after haying been mixed with the salivary 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 organic matters 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 tlay, 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 ted 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 cesophagus; 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. QRGANS OF MASTICATION AND DEGLUTITION. 
1. Tae Moutu. 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 
890 
