CHAO: DIGESTIVE SYSTEM OF CUNNER 



very dense eccentric nucleolus (Figure 18). 

 Granular wandering cells occur in the mucosa, 

 submucosa, and muscularis (Figures 13, 14, 

 18), and are most abundant in the submucosa 

 at the base of the mucosal folds. In the mucosa 

 they are found in both the supranuclear and 

 infranuclear zones. These cells are packed with 

 basophilic granules. The nuclei are always 

 pushed to the cell margin by the large granules 

 (Figure 18). Some of the granulocytes present 

 in the mucosa have very large compact inclu- 

 sion bodies (Figures 14, 18). The polymorpho- 

 nuclear leucocytes represent one type of wan- 

 dering cell (Figure 13). Its nucleus has two or 

 three lobes, and there are very fine neutrophilic 

 granules in the cytoplasm. These leucocytes 

 were encountered only in the infranuclear zone 

 and the submucosal layer of the fold. A lympho- 

 cytelike type of cell was encountered also in 

 the infranuclear zone or the base of the epi- 

 thelium. This type of cell has two nucleoli in 

 the clublike nucleus and very little cytoplasm 

 (Figures 14, 18). They also were encountered 

 in the submucosa occasionally. The typical 

 lymphocytes with large nuclei and thin baso- 

 philic cytoplasm were found in the submucosa 

 (Figure 18). At least one type of amoebocyte 

 (Figure 13) was found in the mucosa and sub- 

 mucosa. This type of amoebocyte has a round 

 nucleus with karyosomes applied to the nuclear 

 membrane and rays extending from the nu- 

 cleolus which is often eccentric. Numerous 



spherical granules and vacuoles occur in the 

 cytoplasm. There are no significant differences 

 in the distribution or types of wandering cells 

 in the submucosa throughout the intestine. 



MUSCULARIS AND SEROSA.— The typi- 

 cal vertebrate muscularis of inner circular and 

 outer longitudinal smooth muscle j^revails in 

 the intestine of the cunner (Figure 11). A very 

 thin layer of smooth, longitudinal muscle fibers 

 (no more than two cells thick) can often be 

 seen inside the circular muscle layer. These 

 fibers appear at random in the first three sec- 

 tions of the intestine and become more promi- 

 nent (two to four cells thick) from the S-loop 

 to the rectal valve. A nerve plexus usually 

 can be found between the muscle layers. The 

 serosa is of a more uniform thickness than that 

 in the esophagus and abuts directly on the 

 extended muscularis. 



Rectal Valve and Rectum 



A muscular flap valve is present at the 

 juncture of the intestine and rectum. The 

 rectal valve is formed by a folding of the circular 

 muscle layer and is not a sphincter valve of 

 thickened muscularis. The two layers of the 

 fold are separated by connective tissue (Figure 

 19). This layer of connective tissue contains 

 granular cells which are more abundant in the 

 submucosa of the rectal side of the valve. The 



sr Im 



':•«•<- 











t 



"^ 



Figure 19. — Intestinal-rectal value of 

 a 210-mm SL cunner (X 40, l.s.). 

 cm, circular muscle; I, intestine; Im, 

 longitudinal muscle: R, rectum; Sm, 

 submucosa; sr, serosa. 



577 



