Paraffin is the agent usually employed for embedding purposes.  Melt it, and add a little lard to soften it; the addition of a little clove oil renders it less adhesive.

Melt the paraffin at as low a temperature as possible, and pour it into a paper cone.  Dip the object into this and remove immediately; as soon as the layer of paraffin surrounding it becomes hardened, replace it in the paraffin; this prevents overheating the tissues.

Where the tissues are too soft to be cut, they may be soaked in a solution of gum arabic and dried; in this condition they can be readily cut, after which the gum can be dissolved off.  This is an extremely useful method for cutting the lung or other organs where an interstitial support is needed.  For a very thin object, a cork fitting any kind of a tube is to be split, and the object placed between the two parts; the cork is then thrust into the tube, and a sufficient degree of firmness will be obtained to allow cutting.  The sections should always be manipulated with camel’s hair brushes.

Much practice will be required before dexterity is attained.

Methods of preserving the tissues.—­All water must be removed from the tissue, either by drying or by immersing it in rectified spirits, and then in absolute alcohol, and the alcohol driven off by floating it upon oil of clove or turpentine.  The substances used to preserve the tissues are Canada balsam, Dammar balsam, glycerine, Farrant’s solution, potassium acetate, spirits, naphtha, and creosote.

The section is to be floated on to the slide or placed in position with a camel’s hair brush.  It should be spread out, and then examined under the microscope for the purpose of improving its position if necessary, or of removing any foreign particles.  A drop of the preserving medium is then placed upon it, and another placed on the cover and allowed to spread out.  The cover is then taken by a pair of pincers and inverted over the object, and one edge brought to touch the slide at one part of its margin.  The cover is then gently lowered, and the whole space beneath the cover filled and the tissue completely saturated.  If air bubbles show themselves, raise the cover at one corner and deposit a further quantity of the medium.

The slide should be set aside for a few days.  First, the excess of the medium must be removed; if it is glycerine, much of it can be removed by a piece of blotting paper, but the cover must not be touched, for it is easily displaced; that near the cover can be replaced by a camel’s hair brush.  A narrow ring of glycerine jelly should be placed around the edge of the cover, to fix it before the cement is applied.  When this has set, a narrow strip of cement is to be put on, just slightly overlapping the edge of the cover and outside the margin of the jelly.  Until it has been perfectly secured, a slide carrying glycerine must never be placed in an inclined position, as its cover will slide off.