118           THE MICROTOMIST 9S VADE-MECUM
of marking-out by staining in various hues the different forms
of tissue. For instance, in a section through the uterus of a
roe-deer, the epithelia are stained blue, the glands dark green,
and the muscle-fibres malachite green, whilst the connective
tissue remains unstained.
In general bone and connective tissue do not take the stain,
gland-cells stain most intensely and selectively, muscle stains
instantaneously and diffusely, but the nuclei are brought out
by their deeper colouration, the sarcolemma remaining un-
stained. Good nuclear stains are obtained with blood, sper-
matozoa, and bacteria (sic).
It is useful for ganglion-cells and for axis cylinders. In
sections of spinal cord, and most especially in sections of
skin, it affords most instructive preparations. In sections of
kidney instructive differentiations are obtained. Chromic-acid
preparations stain well.
On the whole, Griesbach states that "in many respects
iodine-green performs decidedly more than all other anilin         obi
colours employed in histological practice."   "It is the most    teakok
useful of all anilin stains."                                     Tiah
This colour is somewhat expensive to prepare, and for this     10 (1
reason is no longer found in commerce, having been super-        tate
seded by methyl-green. But the high price is no impediment        (g&
to the use of iodine-green in histology, on account of the
small quantity of the substance required for staining.
The presence of iodine may be tested in the following way:
A little of the solid colouring matter is treated with sul-
phuric acid, and a few small fragments of bichromate of
potash are added; the iodine, if present, escapes in the form
of violet vapours. It may also be demonstrated by means of         up
chloroform or sulphide of carbon.
The colour may be obtained of excellent quality from C. A.
F. Kuhlbaum's Chemische Fabrik, Berlin, S. 0.' ('Zool. Anz,'
No. 130 (1883), p. 56.)
1 Dr. Harris found that both malachite and iodine-green are " not at