Hairs of the beard are usually thickest (0.14-0.15 mm. in diameter), then follow in order of size the pubic hairs of the female, the hairs of the eye-lids, male pubis, male head, and female head (0.06 mm. in diameter). There are, however, marked individual differences, and the hair of infants is much finer than that of older children and adults. The hairs of the new-born are pointed, as are also the hairs of adults that are protected from cutting, rubbing, maceration, etc. Cut hairs are at first blunt; later more rounded. Hairs that have been torn out usually show a bulbous end with the remains of the hair-follicle; fallen hairs have a closed, smooth, atrophic root. When the question arises as to the definite individual from whom certain hairs may have come a very careful comparison of the given hairs with those of the individual concerned must be carried out, as to color, size, thickness of different layers, shape and size of the transverse section, etc. Paraffin imbedding should be employed for this purpose. CHAPTER XXX. THE STUDY OF MOUNTED PREPARATIONS. 1. =Preparation.= Analyze the method of preparation of the specimen, noting-methods of fixation, hardening, imbedding, injection, impregnation, staining, etc. Note the reaction of nucleus, protoplasm, red blood-cells and connective-tissue to the stain. Look for special staining reactions (hyalin. amyloid, mucin, etc.) and metachromasia. 2. =Histology.= Look for histologic landmarks by which the organ, or part of the body, from which the specimen is taken can be recognized. If such landmarks cannot be found, analyze the section, element by element, until its histologic features are fully noted and recognized. Answer the question, “From what part of the body does the tissue come?” Carry the differential diagnosis as far as possible, with regard to sex, age, side of the body or organ (for example, in the heart decide as to auricle or ventricle, left ventricle or right, etc.). 3. =Pathology.= Study next the deviations from the normal. Answer these questions: “Is the tissue normal?” “If not, in what respects does it differ from the normal?” Study pathologic conditions with the low power first, then use the high power for the finer details. Consider the histologic features of the organ (capsule, stroma, parenchyma, ducts, etc.) with respect to pathologic changes.