270 ABBEY, ON ORGANIC STRUCTURE. 
pure cellulose, it at once seizes those portions of “formed 
matter’ which come under the head of “ secondary layers.” 
A dye for the structures left uncoloured both by magenta 
and carmine is still a desideratum. 
Although a second characteristic colouring agent thus 
presented itself to me, it did not give a satisfactory contrast of 
colour. Mauve, Hoffmann’s violet, aniline brown, picrate of 
aniline, and turmeric, all dye as magenta, but the purples 
alone approximated to the desired contrast. Aniline green, 
which I subsequently tried, accorded with these, but its results 
hitherto have been capricious and unsatisfactory. It seemed 
probable that a substitute for magenta, if found at all, would be 
found among the aniline colours, and I became indebted to my 
friends Mr. J. G. Dale, F.C.S., and Dr. Martius, who have 
all along most liberally furnished me with dyes not otherwise 
readily obtained—for two blue salts ; the one almost identical 
with magenta, the other belonging to a different though 
closely allied series of compounds. 
I naturally looked to the former, the ordinary aniline blue 
of commerce, for the accomplishment of the sought-for con- 
trast, but it proved a lamentable yet instructive failure. The 
tissue, plunged into its alcoholic solution, came out magnifi- 
cently coloured, and remained so when immersed either in 
water or glycerine. Under the microscope, however, the 
colour was seen to be merely mechanically and impartially 
distributed ; and, by the action of alcohol, its proper solvent, 
it was entirely discharged. This surprise was outrivalled by 
the one which the second blue afforded. The desired con- 
trast was now effected, but at the expense of the carmine, 
instead of the magenta. Nothing could be more satisfactory 
than this result, inasmuch as the blue substitute for carmine 
has intense and splendid colouring power, and is even more 
brilliant by artificial ight than by daylight. It is also freely 
soluble in water, thus incidentally refuting Dr. Beale’s 
somewhat rash explanation of the limited dyeing power of 
carmine, which he refers to the acid reaction of the ‘‘ germinal 
matter” on the alkaline solution of the dye. I feel justified 
in calling this assumption ‘rash,’ because Dr. Beale had 
probably employed no other than an alkaline solution; car- 
mine being only soluble in ammonia, or in a neutral solution 
of oxalate of ammonia, the solvent power of which is not 
generally known. Moreover, such an explanation should be 
based on the reaction, not of the solvent, but of the carmine, 
which, in a good sample, would most likely be acid, owing 
to the presence of free carminic acid. 
