150 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Kleinenberg’s 70% alcohol haematoxylin followed by eosin, and (2) for 
osmic material, the iron haematoxylin as used by Heidenhain.* 
Slides bearing sections of picro-sulphuric material were placed in 
the haematoxylin solution for three or four minutes only ; it was found 
advisable in some cases to dilute the stain with an equal amount of 
70% alcohol. The superfluous haematoxylin was removed with 70% 
aleohol and then the slide was simply dipped into a jar containing 
70% alcohol with a few drops of a sat. solution of eosin in 70% alcohol. 
Cornifying tissues are stained by the eosin bright red, which stands out 
in beautiful contrast with the light blue of other tissues. By this 
method pigment cells and their granules are finely demonstrated. I. 
found, however, with material fixed in the picro-sulphuric mixture a 
slight tendency to shrinkage, which made it inferior to Hermann’s fluid 
for general histological purposes. 
Material fixed with Hermann’s fluid for three hours only was blackened 
superficially ; this was corrected by Weigert’s decolorizer. The iron- 
haematoxylin stain was used in the usual way. 
Feather germs were sectioned transversely, longitudinally, and 
obliquely, and were mounted in Canada balsam. Glycerine was used in 
most cases for mounting sections of dry feathers. 
Teased preparations were also found very instructive, material fixed 
in Hermann’s fluid being especially favorable for such treatment. For 
this purpose a feather germ was first split longitudinally into strips and 
the epidermal portions removed from the pulp. These strips, after be- 
ing stained in toto in haematoxylin followed by eosin, were teased on 
the slide in balsam or xylol. Fully cornified portions were unstained 
by the haematoxylin and eosin, but they retained a light brown stain 
from the fixing fluid. Elements in process of cornification took an eosin 
stain, which was deepest in the more advanced stages, though not ap- 
pearing in the completely cornified elements. Stages preceding cornifi- 
cation took the haematoxylin, as did also nuclei in cornifying portions 
of the feather. . 
Dry feathers have also been studied zn toto, and control observations 
have been made on them to guard against the possibility of overlooking 
a pigment that might be dissolved by the histological reagents used. 
This matter will be brought up later in a discussion of the chemical 
characteristics of feather pigments. ‘ 
Besides Sterna hirundo, feather germs from Passerina ciris Linn., 
1 Picrocarminate of lithium has been used for differentiating cornifying tissues, 
but I have found it inferior to the stains mentioned above. 
