608 THE DIGESTIVE TRACT. 



beneath, and in the mucous layer above, the longitudinal muscle 

 of the mucosa, the latter plexus being situated at the bottom of 

 the tubular glands ; both are connected by oblique branches 

 piercing the muscle-layer. The lymphatics arising from the sub- 

 mucous layer are supplied with valves j they leave the intestine at 

 the insertion of the mesentery. The connective tissue of the peri- 

 toneum possesses a lymphatic capillary system of its own, produc- 

 ing the so-called subserous plexus. The lymphatics form sinuses 

 around the gastric glands (Loven), a number of which are in- 

 cluded between two lymphatics. The uppermost sub-epithelial 

 lymphatics are plexiform, or originate as pointed tubules. Sim- 

 ilar relations are found to exist in the large intestine. In the 

 small intestine the beginnings of the lymphatics are found in the 

 central portions of the villi, either as a wide, single tubule or as two 

 or more longitudinal tubules with transverse connections. Even 

 single tubules may, at the apex, produce a loop, from which, in 

 injected specimens, pointed prolongations between the epithelia 

 are often seen arising. (See Fig. 259.) The lymphatic or chyl- 

 iferous vessels of the villi have a complete lining of endothelia. 

 A closed reticulum of lymphatics surrounds the lymph-follicles, 

 though it is generally believed that, in the rabbit's intestine, 

 the follicles are encircled by a sinus. 



The nerves of the intestines are of both the medullated and 

 non-medullated varieties. They form a plexus above the peri- 

 toneum, and, after having traversed the longitudinal muscle- 

 layer, give rise to the plexus between the longitudinal and 

 transverse muscle-layers (Auerbach's plexus), which is composed 

 of reticular extensions of nerves, with numerous interspersed gan- 

 glionic nerve elements. From the nodular ganglia of this plexus 

 numerous non-medullated nerve nbrillae emanate for the supply 

 of both muscle-layers. A number of nerve-fibers pass through 

 the perimysium of the circular muscle to the submucous layer, 

 where again a plexiform extension is produced, with interspersed 

 ganglionic elements (Meissner's plexus). Its nerve branches sup- 

 ply the mucosa and the muscles of the mucosa. The globular or 

 oblong ganglionic elements are decidedly larger in the submucous 

 than in the intermuscular plexus. (See Fig. 261.) In what man- 

 ner the ultimate nerve fibrillae terminate is not known. 



(7) The salivary glands are large racemose glands which 

 secrete a watery or mucous liquid, and empty either into the 

 oral cavity (the parotid, submaxillary, and sublingual glands), 

 or into the duodenum (the pancreas). According to A. Heiden- 



