hæmatopoiesis (blood-formation), not merely of the corpuscles, but also of certain elements of the plasma (see also p. 304). A more exact definition of its functions is still wanting; we know, however, that extensive nervous, degenerative, and irritative changes occur when it is removed or diseased; the metabolic round is broken or interrupted somewhere, and the name given to the group of symptoms produced is myxedema. GOUT Gout is a disease which has been the battle-field of the humoralists and the anti-humoralists, the former attributing the complaint to some morbid condition of the blood and secretions, the latter to some functional disorder or organic change affecting the solid organs of the body. Owing to the researches of Sir A. B. Garrod,' gout is now placed among the blood diseases; the poison is urate of soda, and most of the symptoms of the disease are owing to the presence of excess of this substance. We have already considered (pp. 252 and 307) the condition of the blood in this disease, and described the methods adopted for demonstrating the existence of the urate in it. Different theories are, however, still held to account for the excess of uric acid in the system, some holding that uric acid is formed in excess, and others supposing that the uric acid formed undergoes imperfect oxidation, and so is not removed from the body. The theory of imperfect elimination is supported by the fact that the amount of uric acid in the urine is very small, and that deposits of urates occur especially in those parts which are not very vascular, such as the cartilaginous and fibrous tissues. It is with these collections of urates in the connective tissues that we have here to deal. The articular cartilages in gout. The metatarso-phalangeal joint of the great toe is that most frequently affected, and a single attack leaves marks behind which are nearly indelible. A deposit first occurs in the superficial parts of the cartilages in the form of fine crystalline needles, forming a more or less close network, and presenting different degrees of opacity. Subsequently the fibro-cartilages, ligaments, and synovial membranes become involved, the entire surface being rendered more or less irregular and covered with chalky deposits, consisting of urate of soda. The synovial fluid may also contain crystals of the same substance. Owing to the infiltration of the ligaments. the joints become stiffened, and may be ultimately distorted and nodulated. 1 Garrod, A Treatise on Gout and Rheumatic Gout; art. 'Gout,' in Reynolds' System of Medicine. Med. Chir. Trans. xxxvii. The crystals in the cartilage can be readily seen in thin sections with a 4-inch objective, and, as a rule, are arranged in star-like clusters. They doubly refract polarised light. The presence of uric acid can be readily demonstrated by extracting slices of the cartilage in water of the temperature of 80°-90° C.; the solution is evaporated in a capsule nearly to dryness with a little nitric acid, on exposure of this to the vapour of ammonia, the purple colour of murexide is seen. Or the aqueous extract may be acidified with a little hydrochloric acid, and crystals of uric acid are deposited in a few hours. If the watery solution be evaporated to a syrup without the addition of any acid, bundles of crystalline needles of urate of soda are deposited. Sometimes similar deposits occur in the arytenoid cartilages, and Cruveilhier found urates deposited in bone itself. Chalk-stones, or tophi.-Collections of urates forming white chalklike deposits occur under the skin in various situations, and if excessive lead to distortions and deformities. An opportunity is occasionally afforded of observing the whole train of phenomena from the commencement to the full development of a chalk-stone. This is most readily done in those which appear upon the helix of the ear. A small vesicle first appears between the skin and the fibro-cartilage; its contents are creamy, and present under the microscope the appearance of a clear fluid in which a number of fine crystalline needles are floating. After some months the vesicle assumes the appearance of a white hard bead, closely resembling a pearl, and it may remain as such for years, or it may grow from an increase of the deposit, and in some cases sets up inflammatory and ulcerative processes. The needles in the early stages after the fluid consistency of the deposit has been lost are found aggregated into small bundles, but later it is difficult to separate them, as they adhere and form a closely interlaced mass. Similar deposits may be found in other situations, such as tendinous aponeuroses of muscles, the sclerotic coat of the eye, and the tarsal cartilages at the angles of the eyes. White nodules on the ears and other parts containing fat and amorphous granular matter, due to the blockage of the ducts of sebaceous glands, must be carefully distinguished from gouty deposits of urates. According to Garrod, chalk-stones consist of urate of soda together with small quantities of animal matter and soluble salts derived from the structures in which the concretions have formed. Possibly in some instances, as in a concretion analysed by L'Hérétier, the calcium phosphate found in large amounts was derived from the tissue; in some cases the sodium urate acting as a foreign body may set up inflammation and become infiltrated with calcium phosphate as tubercular matter often does. Urate of calcium was described as a constituent of chalk-stones by Heintz, and more recently Delépine has found that this salt is more frequently present than is generally supposed. He found it in the urine in cases of gout, and also in the cartilages its typical acicular crystals were present: these give, on being treated with sulphuric acid, a double precipitate of uric acid and calcium sulphate. The kidney in gout.-A deposit similar to those already described often occurs in the kidney, but the crystals of sodium urate are usually larger. Many of the crystals are situated in the connective tissue between the tubules ; some are embedded in the structure of the tubules themselves, and occasionally the tubules are entirely blocked by them, producing white streaks in the pyramids, easily visible to the naked eye (Garrod). Charcot found in some cases that the white matter is partly crystalline, partly amorphous. RICKETS Rickets, or rachitis, is a general disorder which attacks children who are subjected to unhealthy hygienic conditions. One of the most marked effects is an affection of the bones during the process of development. In the part of the cartilage where calcification is occurring there is a great proliferation of the cartilage cells; this leads to an enlargement of the epiphyses. The amount of calcareous matter deposited is deficient in the cartilage, and probably under the periosteum also. The bones are thus soft, and bend, especially if the child be allowed to walk; the deformity so produced is rendered permanent by the subsequent complete ossification that occurs. There is no doubt that insufficient and improper feeding is a very powerful factor in the etiology of rickets. Various observers have studied the influence of food, rich or poor in earthy salts, upon the composition of bone in animals. Forster observed that the amount of calcium diminished in the bones of dogs when their diet contained little or no lime salts. Zalesky 3 and Weiske in similar experiments obtained altogether negative results. By cutting off the salts of lime 1 S. Delépine, Proc. Physiol. Soc. 1887, p. ii. 2 J. Forster, Zeit. Biol. xii. 464. 4 3 Zalesky, Hoppe-Seyler's Med. Chem. Untersuchungen, Heft 1, p. 44. from growing animals some have described the production of a condition akin to rickets (Lehmann), while others have not been able to recognise any rachitic symptoms (Tripier,2 Weiske 3). Equally contradictory views have been held with regard to the influence of the administration of an increased quantity of calcium salts in the treatment of rickets. The most generally accepted view is, however, that the disease is not due to a diminution of the amount of calcium in the food, but to an inability of the disordered alimentary canal to absorb, and of the disordered bone-forming tissue to appropriate the lime which is present. Treatment should therefore be directed, not to increasing the amount of calcium in the food, but to improving the absorptive and assimilative powers of the child by placing it under appropriate hygienic conditions. It has been supposed by many writers that lactic acid is produced in the alimentary canal, and that this plays a part as a solvent of calcareous salts deposited in the tissues. As Gamgee points out, this theory does not rest upon one properly conducted observation, and, like many other crude chemical theories of disease, does not stand the test of even a superficial scientific criticism. He continues as follows: 'Even assuming that lactic acid were generated, this would necessarily be converted into lactates in the blood. No one has been bold enough to assume that the blood loses its alkaline reaction, for no one could conceive of an acid reaction of the blood being compatible with a prolonged continuance of its functions; and yet in order that lactic acid could exert any solvent action, it would be necessary that it should exist free in the blood, or that by an unknown chemical decomposition alkaline lactates should be decomposed in the bones.' The actual alterations that have been found in rachitic bones are as follows:- 1. Their specific gravity falls; the water and organic matter are increased. 2. The amount of fat is increased; but not so much as in the mollities ossium. 3. Occasionally they do not yield normal gelatin. The following analyses of rachitic bones which have been made, show, when compared with those of healthy bone, a very marked 1 Maly's Jahresb. viii. p. 272. Léon Tripier, art. 'Rachitisme,' Dict. encycl. des sciences médicales, Paris, 1874. 5 Weiske, Zeit. Biol. vii. 179 and 333. Gamgee, Physiol. Chem. p. 283. ♪ Gorup-Besanez, Lehrbuch, p. 635. contrast. For the purpose of comparison I take some analyses by v. Bibra of the bones of a child æt. two months. MOLLITIES OSSIUM, OR OSTEOMALACIA This is a disease, occurring in the adult, resembling rickets in causing a softening of the bones. It differs fundamentally from rickets, which affects bones in process of development, in being a morbid process in which the absorption of the salts of fully formed bone takes place. The medullary spaces are much enlarged, and are filled in some cases with red, in others with yellow marrow, and in other cases still with jelly-like connective tissue, such as occurs in the vitreous humour. Lactic acid, as in rickets, has been supposed to be the materies morbi, but the evidence upon which this assertion rests is as unsatisfactory and contradictory as in the case of rickets.2 The chief facts derived from examination of the bones in these cases are 1. The increased proportion of organic matters. 2. The very greatly increased proportion of fat. 3. The corresponding diminution in the mineral matters. 4. In some cases, the bones do not yield gelatin. 5. The bone in some cases is stated to have an acid reaction. The following analyses of the bones from cases of osteomalacia have been made:-3 1 Quoted from Charles' Physiol. and Pathol. Chem. p. 305. E. Schmidt, Annalen d. Chem. u. Pharm. lxi. 142; Heitzmann, Maly's Jahresoericht, iii. 229; Heiss, Zeit. Biol. xii. 151. 5 I am indebted for this table to Gamgee's Physiol. Chem. p. 281. |