I have originated a much better method which is in use in my laboratory, and can be applied to the staining of frozen sections of fresh tissues in large numbers for class use. The sections are floated from the salt-solution on to a warm solution of New Orleans baking molasses diluted ten times, or a dilute sugar-dextrin solution, and thence are floated on to a clean glass plate and arranged in rows. The plate is drained, and then without drying is immersed in absolute alcohol for 15-30 seconds; it is then flooded with a thin celloidin, drained, the celloidin film allowed to set, and the plate then put into warm water, where the celloidin sheet floats off, carrying the sections, which can now be cut out and treated as single celloidin sections, or the whole sheet can be carried through the staining, dehydrating and clearing solutions to be cut up into single sections before mounting. CHAPTER XIX. THE PRESERVATION OF MACROSCOPIC PREPARATIONS. For preserving gross objects for museum specimens alcohol or formol may be employed. The former bleaches the tissues so that ultimately they are almost destitute of color. Formol in a 5 per cent solution gives better color-effects than alcohol, as the blood-containing parts remain darker. The fluid also remains clear and the tissues are firm. When alcohol is used the fluid must be frequently changed, as it becomes turbid and yellowish, and the tissues finally become soft and lose their form. The best methods of preserving the natural color are found in the various modifications of the =Kaiserling method=. The organs or tissues are placed first in a formol solution until they are just hardened, the formol changing the oxyhæmoglobin into acid hæmatin. They are then transferred to alcohol to bring back the natural color, which is accomplished by the change of the acid hæmatin to an alkali hæmatin, which has a color very closely resembling that of oxyhæmoglobin, so that the natural color is approximately reproduced. The method is carried out as follows:— Sol. I.—Formalin 200 cc. Water 1,000 cc. Potassium nitrate 15 grms. Potassium acetate 30 grms. The tissues are left in this solution, in the dark, for one to several days, being watched carefully to see that they are not over-hardened. Sol. II.—80 per cent alcohol for 1-6 hours and then 95 per cent until the color is fully restored (2-24 hours). Watch carefully and remove as soon as best color effect is reached, and preserve in— Sol. III.—Glycerin 400 cc. Water 2,000 cc. Potassium acetate 200 grms.