1883.] Changes which take place in them during Secretion. 27 



increases chiefly in the outer region of the cells, and the granules 

 disappear from this region ; so that an outer non-granular zone 

 and an inner granular zone are formed. The network stretches 

 throughout the cell in all cases : in the outer zone its meshes 

 are filled with hyaline substance ; in the inner zone its meshes 

 are filled with granules and a small amount of hyaline substance. 



The glands in which an outer non-granular zone is not formed 1 

 during secretion are, most of the gastric glands of the frog and 

 toad ; the gastric glands of the snake, and the liver of mammals. 



In the gastric glands of the snake, the decrease in the granules, 

 and the increase of the hyaline substance, is equal or nearly equal 

 in all parts of the cell. In the gastric glands of the frog and 

 toad, whilst the same changes are most marked in all parts of the 

 cell, they go on most rapidly in a narrow strip next the lumen. 

 In the liver cells of mammals, the changes are most active in the 

 central part of the cells around the nucleus. 



It is to be remembered that there is reason to believe, that the three 

 parts of the cell are continually being formed and changed into other 

 substances; the extent of the change which can be observed in a cell 

 during secretion depends upon the relative rates at which these processes 

 go on. I have previously pointed out 2 that different gland-cells vary 

 considerably with regard to the different relative rates at which the 

 formation and breaking down of their constituents take place. 



The differences shown by the different cells after the same 

 treatment, depends, partly upon the different chemical characters 

 of the framework, hyaline substance, and granules in the different 

 cells, and partly upon the different arrangement of these con- 

 stituents. With regard to the former of these causes of difference 

 a few instances may be given. 



In the rabbit's sub-maxillary gland, after treatment with osmic 

 acid, the granules are indistinguishably mixed with the hyaline 

 substance ; and the resulting mass differs so little in refractive 

 and staining power from the network, that the nodal points only of 

 the network are at all distinctly seen. 



In the chief-cells of the cat's gastric glands, after treatment 

 with osmic acid, the granules and hyaline substance are also 

 indistinguishable ; but the network is much more distinct than 

 the network in the rabbit's sub-maxillary gland. The network is 

 however much less distinct than in a gland that has been treated 

 with chromic acid. 



In the chief-cells of the bat's gastric glands, after treatment 

 with osmic acid, the granules are perfectly distinct, but they are 



1 The gastric glands of birds have not as yet been examined for the changes 

 occurring in digestion. Cf. however Nussbaum, Arch. f. mic. Anat. xxi. p. 297, 1882. 



2 Trans. Royal. Soc. Part m. 1881. 



