116 The Cardiac Glands of Mammals 
mass of secretion contained within a cell is incompletely divided into 
two masses by a strand of reticular protoplasm stretching across the 
cell (Fig. 3, A). In such cases the proximal mass of secretion usually 
contains a protoplasmic network composed of thicker trabecule than the 
distal mass. This transverse band is particularly obvious in specimens 
stained by Heidenhain’s 
iron hematoxylin method 
and is of frequent occur- 
rence in all the mucin- 
forming elements of the 
stomach as well as in the 
cells of the glands of 
Brunner (Zimmermann. 
Fie. 38. Three tubules from cardiac glands of man. x 1000. A, Mucous tubule 
in which cells are in early stage of mucin formation. B, Mucous tubule showing 
cells in various stages of mucin formation. Subdivision of mass of secretion into 
two masses by transverse bridge of protoplasm and the gradual disappearance of the 
latter as the proximal mass increases in size. CC, Tubule formed of cells of the type 
of the chief cell of the body of the fundus gland, showing zymogen granules in the 
distal zone and prozymogen (basal filaments) in the proximal zone. D, Binucleate 
parietal cell with intracellular secretion channels. 
98) and in mucous cells from other sources, Maximow, or. As the cell 
fills with secretion (Fig. 3, B), the distinction above referred to between 
the protoplasmic framework of the two masses of secretion gradually 
disappears and the transverse band which separates them becomes dis- 
integrated and may finally disappear, although, as a rule some slight re- 
