290 
NOTES AND MEMORANDA. 
green.* Tlie section is stained in a small dish containing alcohol, to 
which a few drops of eosin have been added. Time various; from 
half an hour to several hours ; being left too long in the eosin is not 
detrimental. The section is then rinsed in water, whereby it loses 
some of the eosin, and is then laid in a watch-glass filled with a solu- 
tion of one of the other colours, and allowed to remain some minutes 
till it is coloured very deeply, almost black. After the section has 
been again rinsed in water, it is jdaced in alcohol, which possesses 
the property in a very high degree of dissolving both the colours. 
This is the most critical part of the process, i. e. hitting the right 
moment when both the colours have been just sufficiently drawn out. 
It is a good plan to take the section out, and view it in oil of cloves 
under the microscoj)e, and if found too deep, to replace it in the 
alcohol. In general it is better to remove the prei)aration when 
still too blue, as the eosin is drawn out somewhat quicker than the 
other colours. The oil of cloves, in which the preparation is put 
after the alcohol, does not affect the eosin, whilst it dissolves (in a 
somewhat different degree of intensity) the other colours. Any desired 
relation between the colours can thus be obtained. When the proper 
tint is reached, the oil of cloves is sucked out as completely as 
possible by blotting-paper (the best plan is to lay the paper on one 
side of the preparation on the stage, and place the stage slanting), then 
apply Canada balsam dissolved in chloroform for a covering. In this 
no further change takes place. If too much oil of cloves is left behind, 
a further extraction of the blue takes place, and the object is surrounded 
by a blue halo. This should therefore be carefully avoided. 
As to the distribution of the colours over the different parts of 
the tissues, the blue (or the green) j)igment stains principally the 
nuclei of the cells, and the eosin the cell-bodies, and attention may 
be drawn to the various shades of colour which appear in these latter, 
produced by the mixture of the red with the blue pigments, condi- 
tioned apparently by the mixture of the other cell-contents with the 
protoplasm, or by the changes produced in the protoplasm by age. 
With regard to the secretions of the cells, as far as these from their 
soft or firm consistency allow of being distinguished in microscopic 
sections, the former are generally stained more blue, the latter more 
red, often simply eosin red. Thus the contents of the goblet cells, 
whilst still contained in the cells or out of them, appear a deep blue, 
the interstitial substance of the hyaline cartilage light bluish, the 
cell-membrane eosin red, the elastic fibres brilliant red, the connec- 
tive-tissue fibrillae dark rose, the bone deep scarlet ; a very peculiar 
and entirely characteristic colour is shown by the red blood-cor- 
puscles, which are bright scarlet. In the blood of the lower verte- 
brate animals, which have nuclei in their blood-coiqmscles, this 
colour forms a still greater contrast to the deep blue nucleus. The 
staining is so intense that sections of organs whose blood-vessels are 
still coloured with blood-corpuscles look as if injected, so strong is 
the contrast between the scarlet and the other tints. 
* Alcoholic solutions of these do not stain enough to be of use, therefore the 
eosin cannot be mixed with the other colours. 
