51 



Identify as before the four coats, noting the character of the 

 muscular tissue in the muscular coat, the number of layers recog- 

 nizable in it and in the muscularis mucosae. In the submucosa 

 observe the presence of blood vessels, both arteries and veins. In 

 the mucosa are the tubular gastric glands opening, two or three to- 

 gether, into depressions of the surface epithelium. In these gland 

 tubules recognize the two kinds of cells, chief and border cells ; re- 

 call the function of each. Compare the surface epithelium of the 

 stomach with that of the esophagus. If your preparation does not 

 show well the gland tubules and their cells ask the instructor to 

 show you one that does. 



102. Stomach. Dog. Vertical section through the wall, 

 pyloric end. ; stained in toto in paracarmine ; collodion ; 

 sections )x. 



Compare this preparation with loi, recognizing the coats and 

 their structure and noting differences in the muscular coats, espe- 

 cially the increase in the thickness of the inner circular coat, and in 

 the glands of the mucosa. Observe that the pyloric glands differ 

 from the peptic (oxyntic) glands shown in loi in (a) the absence of 

 parietal cells, {b) the longer duct into which several tubules open. 

 Recall the relative extent of the regions occupied by the two kinds 

 of glands. 



103. Zymogen granules. Calf. Vertical section through 

 the mucosa of the cephalic end of the stomach (fourth stomach or 

 abomasum). 1% osmic acid; paraffin; sections fx. No 

 staining or Hcl. carmine (§ 87). 



In the deeper part of the mucosa will be seen the gastric 

 tubules, cut across in various directions and lengthwise. The ends 

 of the cells forming the tubules — the chief cells — toward the lumen 

 of the tubule will be seen crowded with granules of a yellowish 

 brown color. These granules are the precursors of the ferment, or 

 pepsinogen granules. Find a border cell and note that no such 

 granules are contained in it. 



SMALL INTESTINE. 



104. Duodenum. Cat. Transection. Zenker's fluid ; col- 

 lodion ; sections //. Stain with hematoxylin and picro- 

 fuchsin. 



