| Glycerine | 1 ounce. |
| Wood naphtha, or pyroacetic acid | 1½ drachm. |
| Spirits of wine | 1 ounce. |
| Ferrocyanide (yellow prussiate) of potash | 12 grains. |
| Tincture of sesquichloride of iron | 1 drachm. |
| Water | 4 ounces. |
Dissolve the ferrocyanide of potash in one ounce of the water; add the tincture of sesquichloride of iron to another ounce. Mix these solutions gradually together, shaking the bottle well which contains them—it is best to add the iron to the potash solution. When thoroughly mixed, these solutions should produce a dark-blue mixture, perfectly free from any perceptible masses or flocculi. Next mix the naphtha and spirits of wine, and add the glycerine and the remaining two ounces of water. This must now be slowly mixed with the blue liquid, shaking the whole well in a large bottle whilst the two come together. The tincture of sesquichloride of iron is recommended, because it can always be obtained of a uniform strength.
31. Dr. Turnbull used a mixture slightly different from the above, which is made with the sulphate of iron:—
| Purified sulphate of iron | 10 grains. |
| Ferrocyanide of potassium | 32 grains. |
| Glycerine | 1 ounce. |
| Pyroacetic acid | 1½ drachm. |
| Alcohol | 1 ounce. |
| Water | 4 ounces. |
Dissolve the sulphate of iron in one ounce of the water, gradually add the ferrocyanide of potassium dissolved in another ounce, and proceed as above.
32. Dr. Beale also gives us the following carmine injection to be employed in the same way as the blue.[G] Take—
| Carmine | 5 grains. |
| Glycerine, with 8 or 10 drops of hydrochloric acid | ½ ounce. |
| Glycerine (pure) | 1 ounce. |
| Alcohol | 2 drachms. |
| Water | 6 drachms. |
Mix the carmine with a few drops of water, and when well incorporated add about five drops of liquor ammoniæ. To this dark-red solution about half an ounce of the glycerine is to be added, and the whole well shaken in a bottle. Next, very gradually pour in the acid glycerine, frequently shaking the bottle during admixture. Test the mixture with blue litmus-paper, and if not of a very decidedly acid reaction, a few more drops of acid may be added to the remainder of the glycerine and mixed as before. Lastly, mix the alcohol and water very gradually, shaking the bottle thoroughly after adding each successive portion till the whole is mixed. This fluid may be kept ready prepared, and injections made very rapidly with it.
[G] When, however, it is desirable to cut very thin sections of the injected subject, the carmine is sometimes added to a solution of fine gelatine—gelatine one part to water eight parts. But the warm water and mode of proceeding which are used with the size solutions before described will be necessary in this case also.
33. The method of making injections with these colours is the same as with the gelatine mixtures before described, except that no heat is required, and consequently most of the trouble removed. The bottle of the fluid must be well shaken immediately before use; and when the object is injected, we must allow it to remain in a cool place for a few hours before cutting it. Thin sections of the subject may be cut with Valentine’s knife, as before described, and are very beautiful transparent objects. Some of the finer tissues, also, are shown much better by this mode of injection than by the opaque, and are easily mounted by washing in clean water when first separated, and floating upon a slide, where they must be allowed to dry thoroughly. They may then be immediately mounted in balsam, or kept in the dry state until it is convenient to finish them; but in many cases this keeping, if too much prolonged, will injure the object. If it is desired to transfer the section to another slide, it will be necessary to wet it thoroughly with water by the aid of a camel-hair pencil, and then gently strip it off with the forceps. When it is wished to preserve injected subjects in “masses,” it must be done by immersion in spirit, and the sections may be cut at leisure. Most of these transparent objects may be mounted in Canada balsam; but some recommend glycerine or glycerine jelly, as allowing the use of a higher power in their examination, and preserving them in a more natural form.