390 PATHOLOGY muscle to become fat -tissue may point to some defective com bustion in the work done by muscles. In the cases of pseudo- hypertrophic paralysis of the leg-muscles in children we are con fronted with an enormous development of the same process. Other cases of local fat -formation, as in the interstitial tissue of the pancreas or around the kidney, are still more inexplicable. Lipo- matous tumours, where they are congenital, may be referred to an early error of tissue -growth ; where they are acquired, we have usually a coexisting or previous obesity (local or general) to resort to, and the only difficulty is to understand how the lobules of fat came to acquire the delimitation or individuality of a tumour. Degenera- Degenerations. In a nosological outline there is perhaps no tions. more convenient place for some remarks on the general subject of degenerative changes than at the end of sections dealing with the liabilities of obsolescence, the special liabilities of the suprarenal and thyroid, and the larger errors of metabolism. The usual healthy appearance of the most elementary kind of protoplasm is a soft translucent grey ; under the microscope this greyish protoplasm is uniformly and finely granular. From that standard of health there are various deviations, representing various kinds or degrees of degeneration. The chief degenerations are the mucous, the albuminous, the fatty, the calcareous, the caseous, and the amyloid. Mucous. The mucous change proceeds on more obvious physiological lines than most of the others ; it is, as we have seen, the proper destiny of surface-epithelium in many situations ; and we have found also, in treating of myxomatous tumours, that even in these it has not very remote affinities to the hsematoblastic function. A some what obscure form of it, the colloid change, has been mentioned in connexion with cancer of the stomach and breast. Albu- The albuminous change is that which is often found in the large miiious. glandular cells of the liver, kidney, &c., in disorders accompanied by a rise of temperature. The cells are somewhat swollen, and their substance is clouded so as to obscure the central nucleus. Fatty. Merging imperceptibly with the albuminous degeneration is the fatty, in which numerous small droplets appear in the cell -sub stance, which is no longer uniform but diversified with highly- refracting granules ; these droplets are of the nature of fat. In the liver-cells the droplets may run together, so that the liver-cell has the ordinary appearance of a physiological fat-cell. But there is in general a broad line of distinction between the transformation of protoplasmic substance into fat (usually in the connective-tissue cells) and fatty degeneration as above described. The latter occurs under many circumstances. It is an accompaniment of phosphorus- poisoning and of those idiopathic states which run parallel with the former, such as acute yellow atrophy of the liver. It is apt . to occur in the inner coat of arteries in chlorotic subjects, producing yellowish opaque patches, which sometimes give rise to erosions. The arteries of the brain are liable to a similar degeneration more universally and under other circumstances than chlorosis. The very common condition of athcroma of the large arteries (especially aorta) is a more extensive degeneration of a fatty kind, on the basis of antecedent swelling or increase of tissue in the deeper part of the inner coat, or in the interval between the inner and the middle coats. This variety of fatty change is often associated with the production of cholesterin scales, and with a subsequent calcare ous transformation. Although it is most common after middle life, it is not a senile change proper, inasmuch as the most long-lived persons have none of it. Calcare- The calcareous degeneration is most often found in the cartilages ous. of the ribs after middle life ; but, like the atheromatous change, it is not properly senile, as the very aged sometimes have their costal cartilages quite soft. The deposition of lime -salts (carbonate of lime) is in the capsules of the cartilage-cells ; on applying a drop of hydrochloric acid to a thin slice of such cartilage an efferves cence of carbonic-acid gas will occur. Lime is often deposited in the enlarged thyroid of goitre, and it is sometimes found in degen erated areas of the placenta. In the suprarenal it is much rarer than the cheesy degeneration. Fatty tumours in the lower animals, especially in the bovines, are liable to become calcareous ; and the presence of granules of lime is a very common feature (along with the cheesy degeneration to be next mentioned) of the peculiar form of tuberculous .growths of the serous membranes, or tuberculous aodules and infiltrations of the viscera and lymphatic glands, in those animals. In other tumours, of man or of animals, it is much less common. Lastly, foreign bodies lodged in the tissues, and the encysted trichina-parasite in the muscles, acquire a deposit of lime in the thickening of tissue which forms their capsule. Caseous. The caseous or cheesy form of degeneration is the characteristic disintegration that the cells and tissues undergo in tuberculous and scrofulous disease. Collections of pus, as in chronic abscess of the liver or in chronic empyema (pus in the pleural cavity), are liable to the same process of drying up and molecular disintegra tion. In the central parts of hard cancers also it is not unusual to find cheesy areas. A form of degeneration not very unlike the caseous may be observed as a perfectly normal incident in the deeper parts of the placenta. It is by far the most common degen eration of the suprarenal cells, whether in association with general tuberculous disease or not. Under all these circumstances the caseous change follows upon a certain amount of hyperplasia of the tissue, for the maintenance of which there has been no adequate provision in the way of new blood-vessels. The gummatous degeneration of the products of syphilitic infec- Gumm tion is not always easily distinguished from the ca.seous ; but, for tous. the most part, the substance is firmer and more cohesive, as the name implies, less dry and friable in the section, and of a brown colour rather than of the yellowish or fawn colour of cheesy degeneration. A vitreous, hyaline, or waxy degeneration of muscular fibre occurs Vitreoi in the courseof some fevers,as well as in progressive muscularatrophy. The amyloid degeneration is the most peculiar of them all. The Amyl- degenerate substance was thought to be allied to starch (whence oid. the name) on account of the reaction with iodine (mahogany-red), but it is now known to be a nitrogenous principle. "When it is present in large quantity, as in the amyloid liver, it gives the cut surface a peculiar glance, like that of fat bacon, and hence it has been called lardaceous or waxy degeneration. Its proper seat is the walls of the smaller arteries and the capillaries ; these undergo a kind of hyaline swelling, like the swelling of boiled sago, so that the aggregate effect in such an organ as the liver is to make it very much larger, firmer, and more rigid in its outlines. This alteration in the vessel-wall facilitates the escape of the fluid part of the blood ; hence the amyloid change in the kidney is a cause of albuminuria and in the intestine of diarrhoea. In the wall of the intestine the course of the amyloid vessel may be tracked by the mahogany - red line left by iodine. This remarkable form of degeneration of the vessels is associated with long-standing sup puration (especially in diseases of bone), with chronic dysentery, syphilis, arid other of the constitutional states called cachectic. l 12. ERRORS OF THE NERVOUS CONTROL. Reference has already been made to the obscure impli cation of nerve-control in such disorders as Addison s dis ease, Graves s disease, diabetes, and acute yellow atrophy of the liver ; the integrity of the controlling nerve-force may be said to be necessary to the perfect carrying out of the give-and-take of metabolism, or to the full effect of the " ferment " in each of the breaking-up processes. In a subsequent section (p. 393 sq.) reference is made to another controlling nervous mechanism, whose paralysis or dis order is immediately accountable for a very large part of the sum-total of sickness in the world, namely, the . mechanism which regulates the animal heat. The present section will be devoted to a few morbid conditions of the cerebro- spinal system, selected to illustrate pathological principles. Neuralgia and Tetanus. One or two instances of neuralgia and Neur- of tetanus will serve to illustrate a peculiarity of the disorders of the algia. nervous system among morbid processes of the body. A person in getting up from a stooping posture before the fire hits the right eyebrow hard against the edge of the mantelpiece ; the blow has touched the filaments of the supra-orbital nerve, and there is more or less of pain for a time over the limited area to which these small sensory twigs are distributed. Several weeks afterwards, when the accident had been forgotten, there is an attack of severe neuralgia over the whole of that side of the face ; the pain shoots along all the nerve -branches above the eyebrow, along all the branches below the eye-socket (infra-orbital), and along the branches going to the skin of the lower -jaw region or chin. The sequence of events means that the injury to the branch of the trigeminus above the eyebrow has touched the trunk of the nerve in such a manner that, after a considerable interval, intermittent attacks of pain are felt along all three sets of branches covering the whole of one side of the face. In other words, a molecular condition of nerve, originally peripheral and limited, has become central and diffusive. Another instance is as follows. A person seated at a high desk day after day exposes the outer side of the ankle and region of the Achilles-tendon to currents of cold air from the opening and shut- 1 See Cl. Bernard, Nouvelle fonction du Foie, comme Organe pro- ductcur de Matiere sucree, Paris, 1853, and Lemons sur le Diabete et la Glycogenese animale, Paris, 1877 ; Pavy, Researches on the Nature and Treatment of Diabetes, Loud., 1S62 ; Senator, Die Albuminurie, Berlin, 1882; Cohnlieim, Ally. Path/il., vol. ii., Berlin, 1881; Grainger Stewart, Practical Treatise on Brig/it s Disease of the Kidneys, Edin., 1868, and in Trans. Internal. Med. Congr., Loud., 1881, vol. ii. ; S. Rosenstein, Die Pathologic vnd Tlvrapie der Xierenkrankheiten, Berlin, 1863,andin Trans. Internal. Med. Congr., Lond., 1881, vol. ii. ; Garrorl, Treatise on Gout, &c., 3d ed., Lond., 1876, and on " Eczema and Albu minuria in relation to Gout," in Trans. Internal. Med. Congr., Loud., 1881, vol. ii. ; Virchow, "Lipoma," iu Krankhaft. Geschicti .ste, vol. i.
