The Nature of Oxyphilic Granulation. 67 
is apparently identical with that of oxyphilic granulation . It would 
appear that we have here not a true stain, in the sense of solution, 
but rather a case of condensation of the stain on the surface of 
colloidal particles. 
The reaction thus detailed for eosin, is obtained also with 
Fuchsin S., though the eosin has a more marked color change, due 
to the loss of fluorescence. The experiment with the dilute solu- 
tions is comparable to the conditions under the microscope, where 
the thin layer of the specimen corresponds to the extreme dilution 
of the solution, and the visible staining of any tissue indicates a 
selected accumulation of such stain. 
It has been shown that the granules of the eosinophile leuco- 
cytes contain iron, and it would seem that the reaction of these 
granules with eosin and fuchsin was due, in part at least, to this 
iron content. 
The affinity of haemoglobin for eosin is possibly dependent 
similarly upon its iron content. 
Copper gives a similar reaction. The color change is, however, 
not quite the same, in that instead of a rich blood-red, the copper- 
eosin has a distinct purplish or bluish tinge. 
Potassium bichromate gives the reaction though very weakly. 
This is suggestive, perhaps, of the effect of fixation by means of 
chromates. 
In insufficiently stained blood smears, the granules of the 
eosinophiles, while characteristic in color, are superficially stained. 
It is not probable that the stain depends upon a selective 
affinity, whereby an accumulation of dye is produced within the 
substance of the granule. It would appear, rather, that this 
reaction is of the physico-chemical sort, and occurs chiefly at 
the surface, between the more solid granule and the solution of 
stain. 
