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Lesson XXL 

 DIGESTIVE TRACT (Concluded). 



(a) CEsophagus. 



The (LMOt)lui;j;iis of u do^ was hardened in aU'oliol, stain(;d in 

 borax carmine, embedded in parallin, and cross-secLloned. Fix to 

 the slide, and mount in l)al.sam. 



Study first under low power, and notice the stratified 

 pavement e[)itheliuni resting on a pa[)illated mucosa, 

 wliicli is limited externally by a muscularis mucosa. Then 

 follows the subtnucosa, 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 CEsophagus and Cardiac End 



of the Stomach. 



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

 the (L'sopliagns and cardiac end of the stomacrli, was- removed, 

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

 small piece including the oesophagus and cardiac end of the stomach 

 was cut out, stained in borax carmine, embedded in paraffin, and 

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



Study under low power. The oesophageal portion of 

 the section shows the structure seen in i^reparation (a) of 

 this lesson: the epithelial lining is stratified pavement 

 which 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 



