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The German objects prepared by imbibition and transparent injection, imported and

         exhibited by Messrs. Smith, Beck & Beck, are extremely beautiful and instructive.
It is now clear that “imbibition” was an early term synonymous with (carmine) staining.

         In addition to the examples designated “INJ” or “IMB”, many of the slides carry no
such designation on the labels (Fig. 1): this applies to over half of the nearly 50 examples
in my own collection. All the examples prepared using carmine imbibition are clearly
marked “IMB” on the labels. Some examples are marked both “IMB” and “INJ” on the
same label (Fig. 4E), and were prepared using both carmine imbibition and transparent
injection. All of my unmarked examples were found to be transparent injections.

         One of the earliest explanations of transparent injection methods is found in
Lecture VII given by Beale during the winter of 1856, and published in 1857 [21]. The
method is based on injection of vascular tissue structures using extremely fine-grained
coloring matter (at the time, primarily Prussian blue and carmine), dissolved or
suspended in a gelatine solution or glycerin. A brief mention of the technique is also
noted in Ure’s 1839 Dictionary [22], under “isinglass”:

          A solution of isinglass coloured with carmine forms an excellent injection liquor to the

This early mention of a carmine-based injection fluid is noteworthy, suggesting that it
was a method already in use for some period prior to 1839.

          This is in marked contrast to many of the surviving slides produced by injection
during the 1840s and 1850s. The injected slides commercially produced during that
period are almost invariably opaque injections prepared using vermilion (Chinese red) or
chromate of lead (chrome yellow) pigments [23], although other coloured pigments were
occasionally used (Fig. 5G-M). These mounts required use of reflected light for study, and
provided limited useful information. The opaque injected tissues were usually presented
on slides in fluid-filled deep cells, or as thick sections mounted in Canada balsam.
Variations of these types of mounts were made famous by early professional slide makers
such as C. M. Topping and Alexander Hett (Figs. 5G-K). In fact, both Topping and Hett
won awards at the The Great Exhibition of 1851 for their preparations of opaque injected
histology specimens [24, 25].

         Although the majority of commercially prepared injected mounts in the early
1850s were still being made using various opaque colours, it is clear there was a growing
interest in the use of transparent colours. Perhaps one of the difficulties preventing a
wider use of carmine for this purpose, was the tendency of the colour to “bleed” through
thin vessel walls, thus ruining the specimen [23, 26]. It may have been the examination
of such unintentional accidents that gave rise to the recognition of the potential use of
carmine as a differential nuclear stain (imbibition) [26]. In any event, extensive

9 Originally published in the Winter 2012 Quekett Journal of Microscopy, Issue 41, pages 701-712

                             Republished with permission in Micscape Magazine, March 2016
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