256 PRACTICAL HISTOLOGY. [XXII. 



with small simple papillae. In the deeper part of the mucous mem- 

 brane are several layers of non-striped muscle, the muscularis 

 mucostjB (248, M.M). 



(b.) Outside this is loose submucous connective tissue with a 

 few blood-vessels, and in the dog and some other animals the acini 

 of mucous glands. The ducts of the latter traverse the coats lying 

 internal to the glands, and open on the inner surface by funnel- 

 shaped openings. 



(c.) Outside this, again, is the muscular coat, which varies in 

 the upper and lower parts of the tube, and also with the animal 

 examined. In the upper part there is striped muscle, in the lower 

 part two layers of non-striped muscle, an inner circular and an outer 

 longitudinal. Between the two layers may be seen ganglionic cells 

 of Auerbach's plexus. 



(d. ) Outside all is the fibrous coat or adventitia, composed of 

 coarser connective tissue, with elastic fibres and blood-vessels. 



For the epithelial cells lining the oesophagus see Lesson IV. 5. 



It is to be remembered that there are very great differences as 

 regards the presence of glands in the oesophagus. Some animals 

 have a considerable number e.g., dog and others very few. 



ADDITIONAL EXERCISE. 



5. Other Methods ((Esophagus). Very good results are obtained by harden- 

 ing in absolute alcohol containing methyl-green, the gland-cells being thereby 

 sharply denned (Subeli). 1 Also double stain with borax-carmine (extract with 

 acid-alcohol), then alcohol, and stain again with iodine-green (twenty-four 

 hours), extract with alcohol, embed, cind cut in paraffin. The mucous mem- 

 brane of some animals (e.g., pig) contains lymph follicles, which can readily 

 be detected in a part of the tube stained in bulk in borax-carmine. 



LESSON XXIII. 



THE SALIVARY GLANDS AND PANCREAS. 

 THE SALIVARY GLANDS. 



ALL these glands have not the same structure, hence it is necessary 

 to classify them. 



Mucous Salivary Glands. The sub-maxillary and sub-lingual 

 glands of the dog and sub-lingual of guinea-pig. 



1 Zeits.f. mik. Anat., vii. p. 224, 1890. 



