9 8 



BENS LEY. 



[VOL. II. 



At the end of the gland they are succeeded suddenly by the 

 zymogenic cells. In these the minute structure is obscured 

 by the large amount of prozymogen present. The cells are less 

 flattened than at the earlier stage of development, probably 

 because the initial distention has been compensated by the rapid 

 division and growth of the cells. A number of these cells is 

 represented in Fig. 6, B. They are now somewhat columnar in 



shape, with convex ends projecting into 

 the lumen. The nucleus is round or 

 oval and placed in the center of the cell, 

 though in the more columnar cell it is 

 often nearer the lumen than the base of 

 the cell. The free end of the cell may 

 be seen in sections stained with neutral 

 gentian, to be filled with granules of 

 zymogen. Other granules may be seen 

 at the sides of the nucleus, and a few 

 are occasionally found in the base of 

 the cell. The rest of the cell is oc- 

 cupied by a deeply staining protoplasm, 

 which owes its ability to absorb nuclear 

 stains to the large amount of prozymo- 

 gen present, as may be shown by the employment of Macallum's 

 methods of detecting masked iron. The distribution of the 

 prozymogen determines the appearance of the cell, and three 

 main types are to be recognized ; in the first the stain is diffused 

 through the whole of the protoplasm, but more pronounced 

 at the base and sides of the cell, and on close examination 

 a very finely vacuolated structure may be made out ; in the 

 second the whole or part of the cell exhibits long deeply stain- 

 ing fibrillae ; and in the third type the prozymogen is distrib- 

 uted as small irregularly staining particles throughout the 

 protoplasm. 



All the three main types of cells composing the glands and 

 surface epithelium are still capable of division, and numerous 

 mitoses may be seen in all. 



Oppel's description of the structure of the oesophageal 

 glands of Proteus would apply word for word to these glands 



FIG. 6. Oesophageal gland of 

 Amblystoma larva. A, mu- 

 cous cells; B, zymogenic cells. 

 Zeiss apoch. 2 mm., comp. 

 ocular 8. 



