yee A. B. MACALLUM. 
although it has an affinity for them, and it persists with this 
character for a long time after the stage of the hematoblast is 
passed. I have found that in a large number of the fully- 
formed red cells in the spleen of the larva of 35 mm. length 
the disc contains a quantity of the modified chromatin, and 
from this the iron is readily liberated, but in later stages both 
the number of such corpuscles and the amount of iron in the 
dise which may be liberated by acid alcohols gradually diminish 
and disappear, the hemoglobin of the disc not yielding its iron 
on the employment of such methods. The nuclear chromatin, 
however, of all stages of the corpuscle, readily gives up its iron, 
even when none can be set free in the disc. 
It thus appears that the hemoglobin of the red corpuscles 
and the analogous compound in muscle-fibre are formed in the 
same way, the only difference obtaining between them existing 
in the fact that the pigment of muscle-fibre does uot, in its 
evolution in the developing ovum, comprehend a stage of 
nuclear chromatin. The process by which they are formed is 
a gradual one, and the position of the iron in the molecule 
is apparently changed. The latter result may be partly ac- 
counted for if we consider the composition of chromatin and 
of hemoglobin. Chromatin is an iron-holding nucleo-albumin 
in which the iron is attached to the nuclein, while in hemo- 
globin the iron is held in the hematin molecule, and in the 
transformations which result in the formation of hematin out 
of nuclein, it is but natural to expect that the relations of the 
iron to the molecule should change also. 
In secreting cells, as, for example, those of the parotid, 
Lieberkiinian, and pancreatic glands, a certain portion of the 
cytoplasm gives evidence of the possession of “‘ masked” iron. 
When the cells of the pancreas of an adult Amblystoma are, 
after hardening in alcohol, subjected to the action of the 
glycerine and sulphide mixture for six or seven days at a tem- 
perature of 60° C.,in addition to the reaction for iron obtained 
in the nucleus, one is found in the cytoplasm of the so-called 
“outer zone,”’ in some cases almost as marked as in the nuclear 
chromatin. The extent of the cytoplasm involved in the reac- 
