THE MICROTOMIST'S VADE-MECUM

of a forget-me-not tone when placed on a white ground.             Q61
"It must be neutral. If a drop of acetic acid be added, or        Datte
even if it be exposed to vapour of acetic acid, the solution      i the
takes on a much deeper hue, and its staining powers are
enhanced. Ammonia on the contrary discolours it. . . .
Into a watch-glassful of the above solution (4 c.c. in con-
tent) I bring about a dozen alcohol-hardened sections. di
They remain there for twenty-four hours, in a closed space
saturated with vapour of water in order to prevent the con-      v hpinch
centration of the solution. Mount the stained sections, and     the 1ii
cement the mounts at once in glycerin; for if they are left in   cinlio
excess of glycerin exposed to the air, the stain is gradually    qie(O
drawn out, which does not happen when the air is at once         b de
excluded."                                                         ld
I have translated the directions literally, and must leave     sihn
the reader to make out whether Heidenhain means to direct        togulth
him to take a neutral or a slightly acid solution. Probably       10, W
he means that neutral solutions are to be employed, and pre-      eobtdi
cautions taken to prevent the access of acetic-acid vapour.        hth
But why ?                                                         the stii
147. Quinol6in-Blue (Ranvier's method ').-The. quinolin       O1an9
should be dissolved in alcohol of 36' strength, and the           bia,th
solution diluted with an equal volume of water. (If the           adldEci
alcohol were taken dilute in the first instance, the blue would    bin
not dissolve.)  The solutions employed for staining should be      het
very weak as the quinolin stains very powerfully.               Sddt
After staining, wash and mount in glycerin. When first          selIti0i
mounted, nuclei will be seen to be stained a fine violet,         frel
nerves of a grey blue, smooth muscle blue, protoplasm blue,        ihe
fat deep blue. But after twenty-four hours in the glycerin,        e, so
the aspect of the preparation is changed; the nuclei have          leAts
become colourless; the protoplasm remains blue, and is seen        rati
to contain granulations stained intensely blue; nerves War
remain grey blue, but frequently contain granulations stained       I
I ' Trait6 technique ' (1875), p. 102.             (nit)

122