(_a_) Glycerine and water, 1 to 7 (sp. gr. 1030). (_b_) Pacini‘s solution of chloral hydrate in water (1 in 10). (_c_) Normal saline solution. (_d_) Roussin‘s solution of glycerine 3 parts, sulphuric acid 1 part (by weight), and water so that the mixture shall have a sp. gr. of 1028. (_e_) Saturated solution of borax in distilled water. If distilled water alone be used, the red corpuscles lose their hæmoglobin and become “laked” or “phantom” corpuscles; if the solution be of higher sp. gr. than _liquor sanguinis_, then the corpuscles become crenated and irregular in shape. [Illustration: Fig. 5.--Photo-micrograph of flax fibres, × 250. (R. J. M. Buchanan.)] The technique of examination has to be varied in certain details, according to the material upon which the stain is. Stains may have to be examined upon cloth-fabrics, wood, plaster, metal, or leather. These will be taken separately, and the methods of examination described which will prove most reliable in each case. 1. _Cloth-fabrics._--Cut out a stain, or part of one, and macerate it in a quantity of one of the solvents mentioned above, sufficient for the purpose. If the stain be very small, squeeze with fine forceps one or more drops upon microscope slides for microscopic, and keep the remainder of the solution for spectroscopic, examination. In dyed fabrics, which have been mordanted, the mordant may fix the blood-stain so as to prevent solution, and especially so when the attempts have been made to wash out the stain with soap and water. To make a solution of the stain in such cases it is best to use distilled water to which a small quantity of ammonia or citric acid has been added; in one or other of these the colouring matter will dissolve. 2. _Wood._--Note the kind of wood, cut off a thin shaving and treat with one of the solvents mentioned above. If on wood containing tannic acid, such as oak or elm, the best solvent is a two per cent. solution of hydrochloric acid. 3. _Plaster._--Scrape off some of the stained plaster, and treat as for cloth or wood. 4. _Metal._--If the stain be upon a clean and unrusted metal, _e.g._ the clean blade of a knife, then gently heat the metal on the side opposite to the stain, when the latter, if recent, will peel off or can be easily detached. This requires some care and dexterity. It is easy, however, to scrape the stain off into a watch-glass, and this procedure is necessary when the metal is rusted and the stain mixed with the rust, or when the stain is thin. [Illustration: Fig. 6.--Photo-micrograph of silk fibres, × 250. (R. J. M. Buchanan.)]