218 TAGG—NOTES ON MUSEUM-METHODS 
A. PRESERVING IN. LIQUID MEDIA. 
1. ALCOHOLIC SOLUTIONS. 
a. Alcohol go per cent. 
The alcohol commonly used is strong commercial methylated 7 
spirit about 90 per cent. and free from mineral naphtha. As 
obtained it is somewhat turbid and commonly of a slight 
brownish colour, and I find that specimens are stained if the pre- 
servative is used in this crude state. To prevent this, before 
being used the alcohol is rendered clear by distillation, The 
strength of the alcohol in the process is slightly raised, and varies 
after distillation from 91 to 95 per cent. 
Such strong alcohol, perfectly clear, has been found to give by 
far the best results. It penetrates the tissues rapidly, quickly 
kills the protoplasm, and very readily hardens, the hardening being 
due to dehydration. As with other media, the usefulness varies 
with the class of specimen to be preserved. 
Class I.—Herbaceous Structures. 
For herbaceous structures generally, leaves, tendrils, and 
nearly all flowers, alcohol proves of great value, but particu- 
larly so where the lie and symmetry of the organs as well as their 
shape and firmness are controlled by the turgescence of paren- 
chyma-cells rather than by special strengthening tissues. Speci- 
mens of the kind killed and preserved in any of the aqueous 
media become flaccid and soft, and although the separate organs 
may retain their form, the relationships of the parts are not pre- 
served. Killed in alcohol or by other methods and subsequently 
preserved in an aqueous medium the results are similar, but killed 
and also preserved in alcohol such specimens retain permanently 
the natural shape of the parts and the relationships of symmetry. — 
Not an unimportant factor in these results is the readiness 
with which alcohol wets the surface of the specimen, removing 
from surface-irregularities air, which, if allowed to remain, would 
interfere with the ready penetration of the medium. More 
important is its low specific gravity and its power of rapidly 
dehydrating. Placed in alcohol the specimen as a tule very slowly 
sinks: it is slightly heavier than the medium. This being so, the 
7 
