Anatomy, physiology and hygiene . or which they have an affinity. The action of yeast, in bread-making, is an example of the action of a ferment. Unorganized fermentsare sometimes called enzymes. 112 DIGESTION. 113. The steps by which food is converted into thetissues of the body are : mastication, or chewing ; vnsali- vation, or mixing withthe saliva; deglutition, orswallowing: stomach andintestinal digestion; absorp-tion, the taking up ofthe digested material bythe absorbents (veins andlacteals); circulation, theconveyance of this mate-rial by the blood to allthe tissues; and assimi-lation,
Anatomy, physiology and hygiene . or which they have an affinity. The action of yeast, in bread-making, is an example of the action of a ferment. Unorganized fermentsare sometimes called enzymes. 112 DIGESTION. 113. The steps by which food is converted into thetissues of the body are : mastication, or chewing ; vnsali- vation, or mixing withthe saliva; deglutition, orswallowing: stomach andintestinal digestion; absorp-tion, the taking up ofthe digested material bythe absorbents (veins andlacteals); circulation, theconveyance of this mate-rial by the blood to allthe tissues; and assimi-lation, the appropriationof it by the cells of thetissues, according to theirneeds. 114. The Alimentary Canal is a musculo-membrane-ous tube, which extendsfrom the lips downwardthroughout the trunk, andin adults is about thirtyfeet in length. In it thefood is digested. It islined throughout its en-tire length by a delicatebut firm tissue, which iscontinuous with a similarlining within the air pas-sages, the whole beingknown as the mucous. Fig. Alimentary Canal. M. oesophagus S, , its cardiac , its pyloric VA. vermiform , large , , bile pancreatic , opening of the commonduct into small intestines. mall intestine. Accessory Digestive , liver. P, pancreas. SP, spleen. DIGESTION. 113 This membrane is richly supplied with blood-vessels for its own nourishment, and, in certain parts ofit, these vessels with lymphatics are peculiarly arrangedto carry on the process of absorption. It is well suppliedwith nerves. In addition to the gastric and intestinaldigestive juices which the mucous membrane secretes,it is supplied with a viscid fluid called mucus, whichprotects it and enables its opposing surfaces to glideeasily upon each other in the various movements of thecanal, incident to The wall of the digestivetract is made up of fibrous connectiv
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