logwood is but short, it is desirable that all the sections should begin to be submitted to its action at the same time, otherwise some will become more deeply stained than others. A good plan is to fill a small porcelain jar (§ 14) with filtered water, and into this transfer the sections. Whilst they are settling well down to the bottom, a mixture must be prepared of half a drachm of Martindale’s solution (fresh) to one ounce of distilled water, and everything got in readiness for its immediate filtration. The water is now very gently to be poured off the sections, and if care be exercised this may be done in such a manner as to leave them undisturbed at the bottom, after removing almost every drop of water. The diluted logwood fluid must now be _immediately_ filtered upon the sections, so that they may run no risk of becoming dry. In the present instance the staining may be allowed to proceed for about thirty minutes, and this will be found a convenient time for the immersion of the general run of animal sections. If the logwood fluid be not quite fresh, either a little more of it will have to be added to the water, or the time of immersion must be prolonged until the desired depth of color has been produced. It is well whilst the staining is going on gently to shake the vessel occasionally, so that the sections may not remain in a heap at the bottom, but all be as fully as possible exposed to the action of the dye. When the staining is judged to be complete, the logwood solution must be gently poured off, leaving the stained sections at the bottom of the jar, when they should be quickly covered with methylated spirit, which will _fix_ the colour. We shall now be able to see if the coloration obtained be perfectly satisfactory. If not deep enough, it is very easy again to submit them to the action of the dye for a few minutes longer. If on the other hand, and as more frequently happens, the coloration should be too deep, the excess of colour may readily be removed by transferring the sections for a short time into some diluted acetic acid prepared by adding five drops of the glacial acid to an ounce of water. The action of this should be carefully watched, and when the colour has been reduced to the desired tint the sections may be retransferred to the methylated spirit. Footnote 13: Should the student, however, determine to prepare this solution for himself, he will find a good formula for the purpose in Schäfer’s “Practical Histology,” p 176. Note I.