DIGESTION. 63 



7. The Tongue. This important organ consists princi- 

 pally of muscle, and is literally the most active muscle in 

 the body. It is covered with mucous membrane, and highly 

 endowed with sensibility. The nerves of the special sense of 

 taste belong to the tongue. On its upper surface may be seen 

 a number of little eminences, or papillae, which are freely 

 supplied with delicate nerve-fibres from these nerves. These 

 papillae vary in size. Some are quite small pointed little 

 specks. There is a row of large ones at the back part of the 

 tongue, arranged in the form of the letter V inverted. 



The root of the tongue is attached to the hyoid bone. The 

 three chief functions of the tongue are : It rolls the food 

 about in the mouth, and helps to keep it between the teeth 

 to be crushed ; it is the seat of the sense of taste, and it takes 

 part in the articulation of speech. In the young the tongue 

 is bright red in color. As age advances it becomes paler, 

 excepting at the tip and edges. This organ promptly sympa- 

 thizes with the stomach when in any way deranged. By 

 the appearance of the tongue the physician is guided, not 

 only in ailments of the stomach, but in almost every form 

 of disease. 



8. The Saliva. The mouth is kept moist with fluid 

 secreted by the mucous membrane. The saliva proper is 

 secreted by a number of glands, which are stimulated to 

 action by the presence of food. The saliva will begin to 

 flow before the food reaches the mouth, and sometimes the 

 thought of food will " make the mouth to water." Mixing 

 with the food as it is ground, the saliva assists in bringing 

 it more quickly into a soft, pulpy mass, fit for swallowing. 

 It is a thin, colorless fluid, which acts upon certain parts 

 of the food chemically. 



9. Salivary Glands. The saliva is secreted by three 

 pairs of glands, the parotid, the submaxillary and the sub- 

 lingual. The parotid lies in front of the ear. It has a duct 



