*Fatty degeneration.*--Prepare from patients who have died of exhausting diseases, phosphorus poisoning, &c. Stain in osmic acid. Mount in Farrant’s medium and keep in the dark. *Mucoid degeneration.*--Study in goblet cells of normal intestine or of ovarian cysts. There are no satisfactory selective stains for mucin. *Colloid degeneration.*--Occurs in the thyroid gland, in the tubules of the kidney in many diseases, and the prostate of the old. Stain in safranine. *Waxy or lardaceous degeneration.*--Best studied in liver, spleen, or kidneys. It should be searched for in persons who have died from a long illness, accompanied by suppuration, _e.g._, phthisis or bone disease. Mount one section unstained, stain another in methyl violet, a third in a weak solution of iodine, and examine the latter at once both by transmitted and reflected light. The iodine stain is not permanent. Another section should be stained in osmic acid, followed by methyl violet, as waxy and fatty degeneration frequently co-exist. *Hyaline degeneration.*--Seen in the arterioles of the spleen in some cases of typhoid and diphtheria. The ordinary staining methods must be used. *Calcareous degeneration.*--Occurs after fatty degeneration in gummata and in atheromatous arteries. It also occurs in the matrix of the costal cartilages after middle life. Mount one section unstained and examine if possible with the polariscope. Stain others in safranine. *Pigmentary degeneration.*--May be studied in brown atrophy of heart, nutmeg liver, &c. It is also seen well in spinal and cerebral nerve cells of the aged. Harden in Müller’s fluid and mount sections unstained. It will be unnecessary to recapitulate the methods for hardening the various diseased organs as the directions for the normal organs hold good. If the presence of micro-organisms be suspected, harden in methylated spirit or absolute alcohol, but as a rule both for diseased organs and tumours Müller’s fluid will be found the most satisfactory reagent for general use. It sometimes happens, however, that it is inconvenient to wait several weeks, until the Müller’s fluid has hardened the specimen sufficiently, before making sections. In this case the best plan is to make fresh sections, or else to cut a slice about one-eighth of an inch thick, and harden for about three days in plenty of methylated spirit, or in formal (p. 23). *Tumours.*--Müller’s fluid should be employed, unless a more rapid agent is required. Methylated spirit may be used in the case of epithelioma, adenoma, &c., but for sarcoma, myxoma, tumours containing cysts or much blood, Müller’s fluid yields by far the best results. BOOKS OF REFERENCE. Methods in Microscopical Anatomy--_Whitman_. Practical Pathology--_Woodhead_. Textbook of Bacteriology--_Crookshank_. Manual for Physiological Laboratory--_Harris_ and _Power_. Practical Histology--_Fearnley_. Practical Pathology and Histology--_Gibbes_.