BY DR. KLEIN. 135 



CHAPTER X. 

 ORGANS OF DIGESTION. 



Teeth. Polished sections of teeth are prepared in the 

 same way as those of bone. They must be made in various 

 directions. For the study of the development of the teeth, 

 maxillary bones of human foetuses, softened in chromic acid 

 in the way previously directed, must be used. The reader is 

 referred for the description of the structure to the ordinary 

 handbooks of general anatomy. 



Salivary Glands and Pancreas. These organs must 

 be steeped several days in half per cent, solution of bichro- 

 mate of potash and prepared by teasing. Small bits of the 

 fresh glands may be steeped for forty-eight hours in the dark, 

 in one-tenth to one-half per cent, solution of osmic acid, and 

 then either placed in water for a day or two, with a view to 

 preparation by teasing, or hardened in alcohol for the prepara- 

 tion of sections. In either case the preparations, if kept, 

 must be placed in concentrated solution of acetate of potash. 

 The arrangement of the alveoli and their ducts, and the 

 characters of the epithelium of each, can be best seen in 

 sections of glands hardened in alcohol, and stained with 

 dilute carmine. In such sections, the beautiful mosaic of the 

 polyhedral epithelial cells of the alveoli, each consisting of 

 granular protoplasm, forms a striking contrast to the cylindri- 

 cal epithelial lining of the ducts; the latter consisting of pale 

 slender cells, each of which appears streaked in the direction 

 of its length, and contains an oblong nucleus in its outer third. 

 The alveoli are united into groups (lobules) by delicate 

 bundles of connective tissue. In teased preparations, the 

 cellular and fibrous elements of the connective tissue, and the 

 ganglion cells which are m^t with here and there, can be studied. 

 In injected glands, each alveolus is seen to be invested by a 

 delicate and very abundant network of capillaries. 



Mucous Membrane of Mouth, Tongue, Pharynx, 

 and (Esophagus. The structure of these mucous mem- 

 branes can be well seen in sections of organs hardened in 

 chromic acid. 1 For studying the epithelium, the papilla, the 

 glands, and muscles, this mode of preparation is sufficient. 



1 As regards the tongue, see also the chapter 011 Organs of Special 



Sense. 



