PATHOLOGY normal obsolescence. Its secreting mechanism becomes finally broken up, so that one may find little left besides traces of the larger ducts in the midst of wide areas of fibrillar tissue and fat. Traces of the glandular structure persist to a very various extent in different women, and even in different parts of the same breast. It is obvious that the process is one which offers numerous oppor tunities for a devious course ; it may be retarded, or advance un equally, or be in the end incomplete. That which in all cases must be held to create the peculiar liability to cancerous infection is the readiness of the preponderant connective tissue to be acted on by epithelial cells dispersed throughout it or otherwise in direct contact with its corpuscles. 10. SPECIAL LIABILITIES OF THE SUPRARENAL AND THYROID. (1) Of the Suprarenal Addison s Disease. The peculiar condition of ill health always fatal which Addison dis covered to be associated with caseous degeneration of both suprarenal bodies was described by himself as " anaemia, general languor and debility, remarkable feebleness of the heart s action, irritability of the stomach, and a peculiar change of colour in the skin." Some of these symptoms appear to be due to interference with the function of the sympathetic nervous system ; the disease, as a whole, however, is almost certainly the direct effect of withdrawal from the general life of the body of those services which the suprarenals are adapted to render. Where there is no caseous degeneration (and consequent non- circulation of blood) in each of the suprarenals the peculiar group of symptoms constituting Addison s disease does not occur ; there may be hyperplasia (struma suprarenal is) of one or both suprarenals, or even true cancer of one or both, but these morbid conditions do not seem to be able to produce the same effect on the organism which is produced by caseous degeneration. On the other hand, Addison s disease lias resulted in a few cases where the suprarenals had not been destroyed by caseous degeneration, but had undergone extreme atrophy. We shall best approach this somewhat intricate disease by considering it from the point of view of suprarenal function, and of the peculiar relation of the present probable function of the organ to its past morpho logical history. Supra- Evidence of Suprarenal Function. A simple experiment will renal show that the blood passing through the suprarenal receives im- blood. portant additions. If the organ taken quite warm from a recently- killed animal, such as the horse, be cut into pieces and placed in a solution of potassium bichromate the central region assumes a rich brown colour. Under the microscope the brown colour will be found to reside in the coagulated plasma filling the numerous lacunar spaces and large veins of the central region and in the cells adhering outside their walls. At the same time it will be seen that the groups of red blood-disks, wherever they occur in the coagulated plasma, form areas of bright green colour. These colour-reactions with chromium are not known to occur anywhere else in the tissues and fluids of the body ; there is that in the out going blood of the suprarenal which reduces the orange-red chro mium-salt to a brown oxide, and (in the case of the red blood-disks with more oxygen) to a green oxide. It will hardly prove an easy task to isolate the substance whose existence is thus indicated, but it is not difficult to follow in the suprarenal structure the adaptations for supplying some such substance to the blood. It is precisely analogous to the adaptation of the placenta, as described above (p. 374), for supplying its metabolic product to the blood destined for the fcetus. Several arteries reach the suprarenal all round its circumference ; they break up into capillaries which radiate to the centre, carrying the suprarenal cells closely adherent to their walls ; towards the centre certain lacunar spaces form, and from these the central outcarrying vessel receives its blood, being provided with contractile muscular walls (in man, the horse, &c. ). Whatever is added to the blood passing through the suprarenal must come from the suprarenal cells. There is reason to suppose that this addition is an actual exuded plasma, just as it is in the placenta. In the latter case the added fluid drops from the protoplasmic wall of the vessel into the circulating blood ; in the suprarenal a membrane is interposed between the lumen of the vessel and the cylinders of secreting cells, namely, the wall of the vessel itself. In this respect the suprarenal cells are as well placed for contributing to the blood flowing past them as are the liver-cells for exercising their glyco- gcnic function. We shall conclude, at least, that the suprarenal blood has received additions whilst in the organ, and that these additions have been a material exudation (plasma) from the supra renal cells. The caseous or putty-like or cretaceous change which overtakes the Addi- suprarenals in Addison s disease involves the complete suppression son s of this function, for it practically amounts to the arrest of circula- disease tion through the organ ; blood neither enters the organ nor passes out of it, and there can be therefore no metabolism. Whatever be the nature of the services that this remarkable organ is adapted to render to the general life, Addison s disease is the evidence that such services cannot permanently be withdrawn with impunity. The most striking effect is the formation of brown pigment, often so abundant as to appear almost black, in the lower cells of the rete mucosum in certain regions of predilection of the skin, and here and there in tlue mucous membranes. Doubtless a large part of the symptoms of Addisou s disease might be traced vaguely to disorder of the sympathetic nervous system ; but, while it is difficult to prove the existence of such disorder of the solar plexus, except as an inference from the symptoms, we have the patent fact that the full train of symptoms in Addison s disease is associated with loss of suprarenal structure and function, including naturally so much of the structure and function of the sympathetic nerve as properly belongs to the organ. The causes of the molecular decay of the suprarenals and conse quent cessation of their function are various. It may be the mere contiguity to a lumbar abscess, or. it may be a part of general tuberculous disease in the body, or it may be associated with no extrinsic morbid condition whatsoever. Enlargement seems usually to have preceded the final molecular break -down. The liability of the suprarenals (with or without preceding enlargement) to caseous degeneration must be considered to be somewhat special to the pair of organs, just as the suppression of their function is of special significance for the life of the body. The caseation soon overtakes the whole structure on both sides, so that a relatively small amount of that not very rare degeneration is of fatal import if the suprarenals be the seat of it. There is a good deal of morphological and developmental evidence that the suprarenals are in one sense obsolete, their structure being, however, adapted or utilized for new functions ; associated with this adaptation of the organs we have the peculiar instability of their protoplasm, the absence of any power of recovery, and the very marked and fatal effects that follow the withholding of their contributions to the metabolism of the body. (2) Sjtccial Liabilities of the Thyroid Gland. The thyroid is in The some respects parallel with the suprarenals. Its cells furnish a thyroid mucus-like plasma which is, in the first instance, poured into the gland. closed vesicles of the organ, but is taken up again and carried into the circulation (as Baber s observations tend to prove, Phil. Trans., 1876, 1881) by the lymphatic vessels in their walls. We have now to consider those not unimportant or infrequent morbid condi tions which are associated with the peculiar functional position of this organ. Goitre. The grand disease in which the functional activity of Goitre, the thyroid is implicated is goitre. Under certain conditions of locality a large part of the population become goitrous, that is to say, their thyroids undergo enlargement. (See GOITKE.) There have also been epidemics of temporary enlargement of the thyroid in garrisons. The simple enlargement undergoes a considerable variety of subsequent changes in the different cases : it may be general or partial at the outset, it may become cystic or " aneur- ismal," gelatinous or hrcmorrhagic, it may become fibrous, very generally it becomes petrified at various centres, sometimes there is a kind of osseous framework developed through its substance, and there may be amyloid concretions. These transformations are too many and complex to be entered upon, although they are full of interest for the elucidation of indwelling embryonic tendencies. The primary fact is enlargement of the thyroid among popula tions whose food, water, air, or environment generally has some thing defective or unsuitable. The enlargement of the thyroid means that the organ has greater calls upon its ordinary func tion, that it makes an effort to meet the circumstances of the case. And there can be no doubt that in most cases the effort is successful ; for goitre, apart from the inconvenient size of the thyroid and the mechanical consequences of pressure, is a harmless condition. The subsequent changes in the enlarged organ are the inevitable consequences of hyperplasia ; but the primary enlarge ment is conservative and adaptive. The adaptation has the effect of elaborating from the blood brought to the thyroid more of the mucous substance which it is the office of the thyroid to elaborate, the same being probably returned to the blood more or less directly. There is that in the water, food, or air of these populations, and in the nutrition of men and animals in isolated cases elsewhere, which calls for more of this peculiar metabolism. Myxadcina. Surgeons have in some places practised removal Myxce- of the enlarged thyroid ; and attention has lately been called in dcina. Switzerland to the after-effects of such removals. The connective tissue in all parts of the body has become occupied with a mucus- like substance or lias shown evidence of unwonted functional and
