2. In consequence of its not making the tissues shrink, it does not squeeze the blood out of the vessels and where the organ has been congested before death, we may, by using Müller’s fluid, preserve a natural injection of the capillaries. 3. There is comparatively little danger of over-hardening the tissue and rendering it brittle. 4. Sections of organs hardened in Müller’s fluid are usually firm and easy to manipulate. They do not tend to curl up or adhere to one another as much as those hardened in spirit. 5. It readily permeates the tissues, and hence large portions of organs, or even the entire organ may be satisfactorily hardened in it. 6. It is very cheap. A gallon can be made up for about eightpence. The fluid has however certain slight drawbacks:-- 1. The hardening process is a slow one occupying four to eight weeks. 2. The fluid gives a permanent dingy colour to the tissue. This does not cause any inconvenience for microscopic purposes, but it is a disadvantage when it is intended to preserve the rest of the specimen, as a naked eye preparation. In such cases the organ should be hardened in spirit, carbolic acid, or formal. Müller’s fluid can be used for almost any tissue. It is especially useful for those which contain a large quantity of fluid, or of blood, and is essential for nerve tissues which it is intended to stain by Pal’s method (p. 89). To harden a specimen in it at least twenty times the bulk of fluid must be employed. The fluid must be changed on the third day, and afterwards about every week as may be required. *Methylated spirit* is a very useful hardening agent. It hardens in one to three weeks according to the size of the tissue and the quantity of spirit used. Its disadvantages are:-- 1. It is more apt to overharden than Müller’s fluid. 2. It causes a great deal of shrinking of the tissue and thus squeezes much of the blood out of the vessels. It is most useful in hardening tissues containing much epithelium, _e.g._, kidney, epithelioma, &c. Spirit is also frequently employed to complete the hardening by Müller’s fluid and to preserve tissues after they have been hardened. About ten or fifteen times the bulk of spirit should be used for one of the tissues. The fluid should be changed on the third day and afterwards as required. *Müller’s fluid and spirit.*--This is a useful combination for many purposes. It is made thus:--Müller’s fluid, three parts; methylated spirit, one part. The fluid must be allowed to cool after mixing before being used, and if necessary filtered. It will harden specimens satisfactorily in three weeks. *Müller’s fluid and formal.*--Is an extremely useful mixture made by adding one part of formal to nine of Müller’s fluid. It hardens in a much shorter time than Müller’s fluid and causes very little shrinkage.