(1) The =mouth=, where the food remains about a minute, while it is chewed and mixed with the _saliva_; the saliva changes a portion of the _starch_ to malt sugar. (2) The =gullet=, a tube nine inches long, running from mouth to stomach and lying in front of the spinal column. [Illustration: =Illustrated Study of Food Tract.= FIG. 89.--ORGANS OF TRUNK from the side. _L_, larynx; _th_, thyroid gland; _T_, trachea; _St_, breastbone; _C_, heart; _D_, diaphragm; _F_, liver; _E_, stomach; _I_, intestine; _Co_, colon; _R_, rectum; _V_, bladder. =Question:= Parts of which organs are farther back than spinal column? Compare this figure with colored Fig. 6. FIG. 90.--DIGESTIVE ORGANS, from the front (liver turned up). 1, gullet; 2, stomach; 3, spleen; 4, pancreas; 5, liver (turned upward); 6, gall bladder; 7, 8, 9, small intestine; 9′, junction of small with large intestine; 10, caecum (blind sac); 11, vermiform appendix; 12, 12′, 12″, ascending, transverse, and descending colon; 13, rectum (straight) just below S-shaped flexure of colon. =Question:= Compare with Fig. 89, and colored Fig. 6.] (3) The =stomach=, a large pouch where the food is stored, and from which it passes in the course of several hours, having become semi-liquid, and the _proteids_ having been partly digested by the _gastric juice_, an acid secretion from the small glands in the stomach walls. (4) The =small intestine=, a narrow tube more than twenty feet long, where the _fats_ are acted upon for the first time, and where the _starches_ and _proteids_ are also acted upon, and where, after about ten hours, the digestion of the three classes of foods is completed by _pancreatic juice_ from the _pancreas_, and _bile_ from the _liver_. (5) The =large intestine=, about five feet long, where the last remnant of nutriment is _absorbed_, and the _indigestible materials_ in the food are gathered together (Exp. 9). =The Teeth.=--The main body of the tooth consists of bone-like _dentine_, or ivory. Hard, shining _enamel_ protects the crown, or visible portion. The part of the tooth beneath the gum is called the _neck_, and the part in the bony socket, is called the _root_. The enamel ends just beneath the gum, where it is overlapped by _cement_ of the root. There is a pulp cavity in every tooth (Fig. 91); it contains _pulp_ made up of connective tissue, with nerves and blood vessels which enter at the tip of the root (Exp. 6). [Illustration: FIG. 91.--CANINE TOOTH CUT LENGTHWISE.]