IRON COMPOUNDS IN ANIMAL AND VEGETABLE CELLS. 223 
tion in all the specimens which I examined varied considerably, 
whether according to the stage of secretory activity could not 
be determined after the use of ammonium hydrogen sulphide, 
for this reagent, in a day or two at an elevated temperature, 
causes the zymogen granules to disappear; but in sections of 
the pancreas from the same animal, after these had been acted 
on by sulphuric acid alcohol, then with the acid ferrocyanide 
solution and eosin, the iron-holding area in each cell was de- 
monstrated by the resulting Prussian blue, while the zymogen 
granules were given an intense red stain, and in this case it 
was found that, apart from the granular zone, the cytoplasm 
was uniformly blue. In other conditions of activity the iron- 
holding area was increased or decreased in correspondence 
with the decrease or increase in the extent of the granular 
zone. In the exhausted condition of the gland-cell, that is, in 
which there were but few granules, arranged in the “ border” 
fashion near the lumen of the tubule, the whole of the cyto- 
plasm exhibited the blue reaction, but the latter was less 
marked than when it was confined to a narrow zone in the 
neighbourhood of the nucleus. The relations of the extent of 
the iron-holding area to the stage of secretory activity were 
less easy to determine in the Lieberkiihnian and parotid glands, 
for it is not possible to demonstrate the mucigen in the former 
or the zymogen in the latter as prominently as the zymogen 
granules may be in the pancreas, but in these the iron-holding 
area appeared in all cases to correspond, in the main, with the 
“ protoplasmic” or “outer” zone. In the “mucous” cells of 
the submaxillary gland of the cat and dog only a narrow zone 
of cytoplasm about the shrunken nucleus contains iron, but in 
the large crescents of Gianuzzi in the cat the whole of the 
cytoplasm is iron-holding. In the peptic tubules of Ambly- 
stoma the cytoplasm in the outer half of each cell contains 
iron, and this is also true of the chief cells in the cardiac por- 
tion of the stomach in the dog and cat. In the parietal cells 
in these animals the cytoplasm is absolutely free from iron. 
The iron-holding zone in each chief cell appears to vary in 
extent with the stage of secretion, but I am unable to speak 
VOL. 38, PART 2.—NEW SER. PB 
