necrotic bone appears as soft, friable granules (molecular necrosis) or sequestra, between which living bone or granulation-tissue may be found. The necrotic granules feel like fine grains of sand when the finger is rubbed over the cut-surface. The color depends essentially upon the amount of granulation-tissue present (gray, grayish-red or deep bluish-red). Purulent areas are cloudy, opaque and yellowish. Tubercles appear as round, grayish, semitranslucent areas, with opaque yellowish centers when calcification has occurred. In young subjects the developing portions of the bone (epiphyses, cartilages) should receive especial examination. Note _amount_, _color_ and _consistence_ of bone-marrow. In the young individual the marrow is red; after puberty the red marrow gradually becomes restricted to the flat bones and the short spongy bones, while in the long bones there develops a yellow, fatty marrow. In old age the marrow of the long bones may become brownish, transparent, myxomatous or soft like colloid, or contain large cystoid spaces filled with a thin mucoid fluid or liquid fat. Red lymphoid marrow is found in the long bones in severe anæmias; it is grayish-red or deep red according to its blood-content. In leukæmia the marrow may be red, violet, pink, grayish or grayish-yellow (pyoid); in chloroma the marrow may be greenish. In cachexias the marrow may become gelatinous as in old age. A hyperæmic fatty marrow should not be mistaken for lymphoid marrow; the fatty shine serves to distinguish the former. Cloudy yellowish areas in the marrow point to purulent infiltration. Firm sulphur-yellow masses are gummata. The most important pathologic conditions of the bones are: atrophy, osteomalacia, rachitis, fractures, dislocations, periostitis, osteomyelitis, ostitis, acromegaly, necrosis, syphilis, tuberculosis, actinomycosis, leprosy, exostosis, hyperostosis, hyperplasia, defects, hypoplasia, dwarfism, giantism, neoplasms (primary sarcoma the most common malignant tumor [periosteal, myelogenous, myeloma, lymphosarcoma, chloroma, leukæmia]; secondary carcinoma [primary in mamma, thyroid, prostate, adrenal] also relatively common; osteoma, lipoma, exostosis cartilaginea, fibrosa and ossificans, fibroma, myxoma, lipoma, angioma, chondroma, etc.), cysts, and parasites (echinococcus, cysticercus).