The apparatus required is not necessarily complicated. Reduced to its elements, it consists essentially only of a razor to cut the sections and a dish to receive them. It but seldom happens, however, that the relations of the parts in sufficiently thin sections can be preserved by such a rough-and-ready method, and frequently the object to be cut is of such small dimensions as to render it impossible to deal with it in this way. It is therefore necessary to “imbed” it, so as to obtain a handle by which to hold it, in such a way that it shall be equally supported in all directions. Moreover, since the human hand can only in exceptional cases be brought to such a pitch of skill as to cut a series of sections, or even single ones, of the needful delicacy, some mechanical means of raising the object through a definite distance is highly desirable. The writer has cut many thousands of sections with the “free hand,” but the personal equation is a large one, and is not always the same in the same person. For single sections the method will, with practice, succeed very well, but some means of securing a number of sections of more or less the same thickness is usually required. Let us deal with the imbedding first. If it be desired to imbed a tissue which has merely been fixed with formalin, the block should be immersed in strong gum (made by saturating water with picked gum arabic, white and clean) for several days. It is then taken out and, without draining, transferred to the plate of a freezing microtome, and the sections cut from the frozen block, and mounted in glycerine at once. This plan is of limited usefulness, since it allows of very little differentiation of the tissue elements, and that only optical.