STRUCTURE OF THE MAMMALIAN GASTRIC GLANDS. 871 



but also in the outer protoplasmic zone of the chief cells of the 

 body of the gland. The reaction in the protoplasm is about 

 equal in intensity to that obtained in the oxyphile nucleolus. 

 The best method of demonstrating the presence of prozymogen 

 is by means of the hsematoxylin iron reaction, recently an- 

 nounced by Macallum.^ In this method, after unmasking the 

 iron by means of sulphuric acid alcohol, the sections are carefully 

 rinsed in alcohol to remove all the free acid, then transferred to 

 0'5 per cent, solution of pure hsematoxylin in water, which turns 

 every portion of the section containing iron a peculiar slate-blue 

 colour similar to that obtained in staining by the iron-alum 

 hseraatoxylin method of M. Heidenhain. This is a much more 

 sensitive test than the ammonium hydrosulphide or ferro- 

 cyanide reactions, and serves extremely well to exhibit the iron 

 when present in only minute quantities in the protoplasm. In 

 sections so treated the outer protoplasmic zone of the chief 

 cell shows a distinct blue colour, indicating that it contains 

 a considerable amount of unmasked iron. A reaction is also 

 obtained in the protoplasm of the portion of the cell occupied 

 by the granules of zymogen, although not equal in intensity to 

 that in the outer clear zone. 



The presence of a large quantity of masked iron in the cell 

 protoplasm is a feature which serves to distinguish the chief 

 cells of the body of the fundus gland from all other glandular 

 cells in the stomach. The protoplasm of the border cells 

 shows no reaction whatever when treated in the manner indi- 

 cated above ; and that of the pyloric gland cells, of the cylin- 

 drical surface cells, and of the chief cells of the neck of the 

 gland gives only a faint reaction for iron. 



The prozymogen or cytoplasmic chromatin differs from the 

 nuclear chromatin in" some respects, as is shown by its relation 

 to stains. In sections stained in gentian violet the prozy- 

 mogen takes a reddish metachromatic stain, which contrasts 

 very well with the colder blue of the nucleus and zymogen 

 granules (fig. 4). In Biondi solutions, which give a good basic 

 nuclear stain, the prozymogen stains reddish — not, however, a 

 ' 'Journal of Pliysiology,' vol. xxii, 1897. 



