According to Garrod, the exudations in articular gout are rich in the urates of soda, lime, magnesia, and ammonia; they also contain some phosphate of lime and traces of organic matter. The watery portion is absorbed and the salts are deposited in crystalline forms. The location of these deposits varies: they are found on the synovial surfaces, in the cartilage-cells, and in the intercellular substance; in the tendons, ligaments, and bursæ, and in the subcutaneous connective tissue. The urate of soda occurs not on the free surface of the cartilage, and replacing {116} the latter, as was formerly generally supposed, but as an infiltration into the substance of that tissue; and Garrod found that there is always a thin layer of unaffected cartilage lying between the deposit and the free articular surface--an observation which has been confirmed by Budd and quite recently by Ebstein.[5] [Footnote 5: W. Ebstein, _Die Natur und Behandlung der Gicht_, Wiesbaden, 1882.] Very important are the recent investigations of the latter. After making numerous observations on the cartilages and other affected tissues of gouty subjects, besides studying the disease artificially produced in fowls, he has shown that those portions of cartilage and other tissues in which the deposit occurs are in a state of necrosis, as is evident from the fact that when the urates are dissolved out by warm water the area in which the deposit occurred, though apparently normal to the eye, refuses to be stained with aniline dyes, and lies plainly visible as a light spot in the midst of stained tissue. Since the work of Weigert we know that this is a sure sign of that peculiar form of death of a tissue to which the name of coagulation necrosis has been given. Ebstein regards this necrosis as primary and the deposition of the uratic salt as secondary. According to him, the urates circulating in the blood give rise to necrosis in parts where the circulation is sluggish (as the articular cartilages, the ears, and the extremities generally), and where, consequently, they remain a greater length of time in contact with the tissues. The necrotic portion has, however, an acid reaction, which causes a deposition, from the soluble neutral salt, of an acid urate in a crystalline form. Ebstein claims that this necrotic area, in which there is deposited a crystalline urate of soda, and around which there is a secondary inflammatory zone, is characteristic solely of gout. "I have never seen," he says, "in gout a crystalline deposit of urates occurring in normal tissue."