3. _On Cutting unprepared Animal Tissues._—For the cutting of fresh _animal_ tissues several plans may be followed. Thus, if a section of only very limited area be required, it may be obtained by snipping a piece off the tissue with a pair of bent scissors, which, for this purpose, are so made that the blades are _curved on the flat_ (Carpenter). If this be carefully performed it will be found that a large portion of the section (particularly at the circumference) so obtained will be sufficiently thin for examination. If a larger section be desired, an attempt may be made to cut it with a very sharp scalpel or razor, the blade of which whilst in use must be kept _flooded_ with water, or spirit, the latter of which is to be preferred. Recourse may also be had to _Valentin’s_ knife. This consists of two long, narrow blades, running parallel to each other, the distance at which the blades are held apart, and which, of course, determines the thickness of the section, being regulated by means of a fine screw passing through both blades. A milled head attached to this screw gives a ready means of opening or closing the blades, so as to bring them to the desired degree of approximation. The method of using the knife is very simple. After having “set” the blades at the desired distance apart by means of the milled head, the tissue to be cut is held in the left hand immersed in a basin of water. The knife is now steadily and with a rapid motion _drawn_ through the tissue, care being taken that the cut is made in such a manner that the blades move from heel to point. By slightly separating the blades and gently shaking them in the water, the section at once becomes disengaged. After use, the blades must be thoroughly dried, when they may be smeared with some oil which does not readily oxidize. For this purpose, a very suitable oil is that known as “Rangoon.”[1] Though it has been deemed advisable briefly to describe the preceding methods of cutting unhardened tissues, it will be found that for the purposes of the ordinary microscopical student sections so obtained are of very little value. They are always of very limited dimensions, seldom of uniform thickness, and often so extremely friable as to render it very difficult and frequently impossible to submit them with safety to such further treatment as is necessary to fit them for being mounted as permanent objects. This method of section-cutting, however, is not without its uses, for by its means the medical practitioner is provided with a simple and ready method of roughly investigating the structure of morbid tissues, whilst to the general student it furnishes an easy means of making a cursory examination of certain substances, in order that he may determine whether it be worth his while to subject them to some of those various processes of hardening hereafter to be described. Footnote 1: Note A.