598 



THE DIGESTIVE TEACT. 



surface of the mucosa is smooth, and no villi are perceptible. 



Each villas comprises the following layers: (a) a covering col- 



umnar epithelium / (bjmyxoma- 

 tous connective tissue, forming 

 the central portion of the villas ; 

 in this are imbedded fcj delicate 

 longitudinal (Briicke) and trans- 

 verse (Moleschott) bundles of 

 smooth muscle-fibers j (d) a 

 rich plexus of capillary blood- 

 vessels, and (e) a central lymph 

 or chyliferous vessel. 



The epithelium is of the 

 columnar variety, with numer- 

 ous wedges or intercalated for- 

 mations between the conical or 

 cylindrical bodies. These are 

 separated from each other by 

 an envelope of cement-sub- 

 stance, which is traversed by 

 connecting filaments (see page 

 130, Fig. 44). The cement- 

 substance is well developed on 

 the free surface of the epithe- 

 lia, producing the so-called 

 "basal seam" of authors. This 

 seam consists of a thin and ho- 

 mogeneous layer of cement- 

 substance, studded with a 

 number of short, delicate rods. 

 which are plainly visible only 

 when, by imbibition of a liquid, 

 the epithelium is slightly swell- 



FIG. 255. SMALL INTESTINE OF A DOG. 

 TRANSVERSE SECTION. BLOOD-VES- 

 SELS INJECTED. 



ed. To the presence of these 

 rods Brettauer and Steinach 

 first drew attention, while K611- 

 iker and Funke considered the 

 vertical striation of the basal 



Seam to be minute pore-Canals. 



According to the difference of 

 conception as to the structure 

 of the seam, some physiologists claim that the finest fat-granules, 



V, villi; G, tubular intestinal glands; M, 

 longitudinal muscle-layer of the mucosa; A, 

 lymphatic (adenoid) or submucous layer; -R, 

 Circular muscle of the intestine, cut longitudi- 

 nally ; L, longitudinal muscle of the intestine, 

 P, peritoneum. Magnified 



