A treatise on physiology and hygiene for educational institutions and general readers .. . eak or scratch it—as gritty tooth-powders, metal tooth-picks, andthe shells of hard nuts. Sudden alternations from heat to cold,when eating or drinking, also tend to crack the enamel. 14. Action of the Saliva.—While the morsel of food is cut andground by the teeth, it is at the same time intimately mixed with the saliva, or fluids of themouth. This constitutesthe second step of diges-tion, and is called insali-vation. The saliva, thefirst of the digestive solv-ents, is a colorless, wa-tery, and frothy fl
A treatise on physiology and hygiene for educational institutions and general readers .. . eak or scratch it—as gritty tooth-powders, metal tooth-picks, andthe shells of hard nuts. Sudden alternations from heat to cold,when eating or drinking, also tend to crack the enamel. 14. Action of the Saliva.—While the morsel of food is cut andground by the teeth, it is at the same time intimately mixed with the saliva, or fluids of themouth. This constitutesthe second step of diges-tion, and is called insali-vation. The saliva, thefirst of the digestive solv-ents, is a colorless, wa-tery, and frothy fluid. Itis secreted (/. e., separatedfrom the blood) partly bythe mucous membranewhich lines the mouth,but chiefly by the salivaryglands, of which there are three pairs situated near the mouth. 15. These glands consist of clusters of very small pouches, aroundwhich a delicate network of blood-vessels is arranged; they emptyinto the mouth by means of little tubes, or ducts. The flow fromthese glands is generally sufficient to maintain a soft and moistcondition of the tongue and mouth. Fig. 24.—Structure of a Salivary Glant>. but when they are excited bv teeth are changed by decomposition into lactic acid. Occasional examinationof the teeth is prudent, in order that a commencing cavity may be promptlydetected and remedied. Teeth that are decayed beyond remedy by fillingshould be immediately removed.— Lane on tlte Hygiene of the Teeth. 13. Destruction of the enamel ? How guarded against ? 14. Mixing of food with the saliva ? What is the saliva? How secreted? The salivaryglands? 15. The flow of saliva ? The thought of food ? Anxiety and grief? Animals fed upo*dry and .coarse food ?
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Keywords: ., bookcentury1800, bookdecade1, booksubjectphysiology, bookyear1887
