OF THE 



UNIVERSITY 



OF 



&U.1FOR&I 



LESSON XXI. 

 DIGESTIVE TRACT (Concluded). 



(a) (Esophagus. 



The oesophagus of a dog was hardened in alcohol, stained in 

 borax carmine, embedded in paraffin, and cross-sectioned. Fix to 

 the slide, and mount in balsam. 



Study first under low power, and notice the stratified 

 pavement epithelium resting on a papillated inucosa, 

 which is limited externally by a muscularis mucosa. Then 

 follows the submucosa, a fibrous tissue coat containing the 

 larger vessels. Mucous glands may be seen in this 

 stratum. Next is a muscular coat composed of inner cir- 

 cular and outer longitudinal bundles. If the section is 

 from the upper third of the oesophagus, the muscular tissue 

 is largely of the striped variety, below this, non-striped. 

 Sketch a segment of the wall as seen under low power. 



(b) Junction of the (Esophagus and Cardiac End 



of the Stomach. 



A portion of the alimentary canal, including the lower end of 

 the oesophagus and cardiac end of the fttOfftftafe, was removed, 

 pinned out on a flat cord, and hardened in absolute alcohol. A 

 small piece including the oesophagus and cardiac end of the stomach 

 was cutout, stained in borax carmine, embedded in paraffin, and 

 sectioned. Fix to the slide, and mount in balsam. 



Study under low power. The cesophageal portion of 

 the section shows the structure seen in preparation (a) of 

 this lesson : the epithelial lining is stratified pavement 

 Avhich ends abruptly at the termination of the oesophagus. 

 Large mucous glands are usually found in the mucosa and 

 submucosa. In the dog a layer of striped muscle fibres, 

 which extends as a thin sheath outside of the non-striped 



