146 



ANATOMY FOE, NURSES. [CHAP. XIII 



layer of plain muscular tissue termed the mmcularis mucosce'. 

 this layer is not always present. The connective tissue layei 

 varies much in structure in different parts ; the lymphoid 

 variety is in certain places greatly increased in amount, packed 

 with lymphoid cells, and forms the solitary follicles and 

 Peyer's patches described in Chapter XII. 



The small blood-vessels conveying blood to the mucous mem- 

 branes divide in the sub-mucous tissue, and send smaller branches 

 into the corium, where they form a network of capillaries just 

 under the basement membrane. The lym- 

 phatics also form networks in the corium 

 and communicate with larger vessels in the 

 sub-mucous tissue below. The free surface 

 of the mucous membrane is in some parts 

 plain, but in others is beset with little emi- 

 \OL nences named papillae and villi. 



The papillae are best seen on the tongue ; 

 they are small processes of the corium, 

 mostly of a conical shape, containing blood- 

 vessels and nerves, and covered with epi- 

 thelium. 



The villi are most fully developed on the 

 mucous coat of the small intestine. Being 

 > c ^ set close together like the pile of velvet, 



FIG. 94. -AN INTES- the ^ & ive a sha ^^ or villous appearance 

 VILLUS. a, a, a, to the membrane. They are little projec- 



tions of the mucous membrane, covered with 

 c, c, longitudinal muscle epithelium, and containing blood-vessels 



fibres ;d, lacteal vessel. au( j lacteal ^ ftnd are f avourab ly arranged 



for absorbing nutritive matters from the intestines. 



SECTION II. Food. Under the term "food" we include all 

 substances, solid or liquid, necessary for nutrition. The ques- 

 tion at once arises: What are these substances, and how are 

 they obtained? 



If we analyze the food we daily take into our mouths and 

 introduce into the alimentary canal, we find it separable into 

 two divisions ; viz. that which is nutritious, and that which 

 is innutritions. The nutritious portion, that which can be 

 digested, absorbed, and made use of by the body, is generally 

 spoken of under the name of food-stuffs or food-principles: the 



