976 The American Naturalist. [November, 
real ; for structure is there and it can be made out, although with some 
difficulty. Cell nucleus and cell body, although chemically different, 
exhibit the same morphological structure, consisting of granula and 
inter-granular net-work. Altmann was able to demonstrate the granu- 
lar structure of the chromosomes. 
Heidenhain (Arch. f. mik. Anat., XLIII, 3, p. 428) maintains, in 
opposition to Altmann, that with sublimate the granula and net-work 
are demonstrable; and further, that acid reagents are, after all, supe- 
rior to neutral reagents. 
Iron-hematoxylin and Centrosomes.‘—-Iron-hematoxylin 
has been used by Heidenhain in the study of the centrosomes and as- 
trospheres. 
The original process, which is also repeated in the new modification, 
was the following: | 
Fine sections of preparations in sublimate are fixed on the slide by 
means of distilled water, dehydrated with alcohol containing iodine, 
and exposed to a 13 per cent solution of ammonio-ferric alum? The 
slide is next washed with distilled water and then placed in a 1} per 
cent solution of Hematozylinum purissimum (Griibler). The over- 
stained sections are then again treated with the iron-alum solution used 
before, in order to remove the superfluous color. The process of ex- 
traction must be followed under the microscope and continued until 
the cell protoplasm is completely decolorized, and the chromatin net- 
work of the nucleus becomes clear. One may interrupt the differenti- 
ating process any moment by washing with fresh water, and then con- 
tinue it. When the extraction of the stain has been carried far 
enough, the slide should be washed fifteen minutes in fresh water and 
mounted in the usual way in balsam. 
Heidenhain noticed that when the differentiation was effected 
quickly the centrosomes were stained in greater number than when 
the process occupied a long time. It seemed, therefore, that the de- 
fects of the method might be corrected if a way could be found by 
which the decoloring process could be hastened. How could the cyto- 
plasm be freed from the stain in the shortest time ? Assuming that a 
stain acts by chemical combination, it seemed probable that the pro- 
cess of extraction might be hastened, if the receptivity of the cytoplasm 
could be at least partially saturated before the application of the hem- 
atoxylin. Accordingly, Heidenhain selected as preliminary stains 
“Arch. f. m. Anat. Vol. XLIII, part 3, p. 434. 
"The crystals of this salt should be clear violet in color; if they are yellowish 
and opaque, they have suffered from exposure to air and are no longer fit for use. 
The solution must be made cold, as the salt is decomposed by heat. 
