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Originally appearing in Volume V20, Page 924 of the 1911 Encyclopedia Britannica.
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TISSUE PRODUCTS Mucoid.—In many pathological conditions we have degenerative products of various kinds formed in the tissues. These substances may be formed in the cells and given out as a secretion, or they may be formed by an intercellular transformation. In the mucinoid conditions, usually termed " mucoid " and " colloid " degenerations, we have closely allied substances which, like the normal mucins of the See also:body, belong to the glucoproteids, and have in See also:common similar See also:physical characters. There is neither any See also:absolute difference nor a constancy in their chemical reactions, and there can be brought about a transition of the " colloid " material into the " mucoid," or conversely. By mucoid is understood a soft gelatinous substance containing mucin, or pseudomucin, which is normally secreted by the See also:epithelial cells of both the mucous membranes and glands. In certain pathological conditions an excessive formation and See also:discharge of such material is usually associated with catarrhal changes in the epithelium. The desquamated cells containing this jelly-like substance become disorganized and blend with the secretion. Should this take See also:place into a closed gland space it will give rise to cysts, which may attain a See also:great See also:size, as is seen in the ovarian adenomata. In some of the adenoid cancers of the alimentary See also:tract this mucoid material is formed by the epithelial cells from which it flows out and infiltrates thesurrounding tissues; both the cells and tissues appear to be transformed into this gelatinous substance, forming the so-called " colloid See also:cancer " (fig. 42, Pl. IV.). The connective tissue is supplied normally with a certain amount of these mucinoid substances, no doubt acting as a lubricant.

In many pathological conditions this tissue is commonly found to undergo mucoid or myxomatous degeneration, which is regarded as a reversion to a closely similar type—that of foetal connective tissue (fig. 43, Pl. IV). These changes are found in senile wasting, in metaplasia of See also:

cartilage, in many tumours, especially mixed growths of the parotid gland and testicle, and in various inflam-, matory granulation ulcers. In the wasting of the See also:thyroid gland in See also:myxoedema, or when the gland is completely removed by operatioh, myxomatous areas are found in the subcutaneous tissue of the skin, See also:nerve-sheaths, &c. Colloid.—T his See also:term is usually applied to a semi-solid substance of homogeneous and gelatinous consistence, which results partly from See also:excretion and partly from degeneration of cellular structures, more particularly of the epithelial type. These cells become swollen by this translucent substance and are thrown off into the space where they become fused together, forming colloid masses. This substance differs from the mucins by being precipitated by tannic See also:acid but not by acetic acid, and being endowed with a higher proportion of See also:sulphur. In the normal thyroid there is formed and stored up in the spaces this colloid material. The enlarged cystic goitres show, in the distended vesicles, an abnormal formation and retention of this substance (fig. 44, P1. V.).

Its See also:

character is readily changed by the abnormal activities which take place in these glands during some of the acute fevers; the semi-solid consistence may become mucoid or even fluid. Serous degeneration is met with in epithelial cells in inflammatory conditions and following on See also:burns. The vitality of these cells being altered there is imbibition and See also:accumulation of watery fluid in their cytoplasm, causing swelling and vacuolation of the cells. The bursting of several of these altered cells is the method by which the skin vesicles are formed in certain conditions. Glycogen is formed by the See also:action of a ferment on the carbohydrates—the starches being converted into sugars. The sugars are taken up from the circulation and stored in a less soluble See also:form—known as " See also:animal See also:starch "—in the See also:liver and muscle cells; they See also:play an important See also:part in the normal See also:metabolism of the body. The significance of glycogen in large amounts, or of its See also:absence from the tissues in pathological conditions, is not clearly understood. It is said to be increased in saccharine See also:diabetes and to be greatly diminished in See also:starvation and wasting diseases. See also:Fat.—Fatty accumulations in the tissues of the body are found in See also:health and in pathological conditions; these are usually recognized and described as fatty infiltrations and fatty degenerations, but there are intermediate conditions which make it difficult to See also:separate sharply these processes. The fatty accumulations known as infiltrations (See also:figs. 45 and 46, Pl. V.) are undoubtedly the result of excessive ingestion of See also:food material containing more neutral fats than the normal tissues can oxidize, or these, as a result of defective removal owing to enfeebled oxidative capacities on the part of the tissues, become stored up in the tissues.

In acute and chronic alcoholism, in See also:

phthisis, and in other diseases this fatty See also:condition may be very extreme, and is commonly found in association with other tissue changes, so that probably we should look on these changes as a degeneration. Adiposity or obesity occurs when we have an excessive amount of fat stored in the normal connective-tissue areas of adipose tissue. It may be caused by various conditions, e.g. over-See also:nutrition with lack of See also:muscular See also:energy, See also:beer-drinking, castration, lactation, disturbed metabolism, some forms of See also:insanity, and may follow on some fevers. Fatty degeneration is a retrogressive See also:change associated with the See also:deposit of fatty granules or globules in the cytoplasm, and is caused by disorganized cellular activity (figs. 26 and 27, P1. II.). It is frequently found associated with, or as a sequel to, cloudy swelling in intense or prolonged toxic conditions. Over and above the bacterial intoxications we have a very extreme degree of fatty degeneration, widely distributed throughout the tissues, 922 which is produced by certain organic and inorganic poisons; it is seen especially in See also:phosphorus and See also:chloroform poisoning. The changes are also common in pernicious See also:anaemia, advanced See also:chlorosis, cachexias, and in the later stages of starvation. In diabetes See also:mellitus, in which there is marked derangement in metabolism, extreme fatty changes are occasionally found in the See also:organs, and the See also:blood may be loaded with fat globules. This lipoemic condition may cause embolism, the plugging especially occurring in the See also:lung capillaries. Fatty degeneration is common to all dead or decaying tissues in the body, and may be followed by calcification.

Autolysis is a disintegration of dead tissues brought about by the action of their own ferments, while degeneration takes place in the still living See also:

cell. The study of autolytic phenomena which closely simulates the changes seen in the degenerating cell has thrown much See also:light on these degenerative processes. These conditions may be purely physiological, e.g. in the mammary gland during lactation or in sebaceous glands, caused by increased functional activity. It may follow a diminished functional activity, as in the atrophying thymus gland and in the muscle cells of the uterus after parturition. Any of the abnormal conditions that bring about See also:general or See also:local defective nutrition is an important See also:factor in producing fatty degeneration. The part played by fats and closely allied compounds in normal and abnormal metabolism need not here be discussed, as the subject is too complex and the views on it are conflicting. It will be sufficient to See also:state briefly what appears to be the result of See also:recent investigation. The neutral fats are composed of fatty acids and See also:glycerin. In the physiological See also:process of intestinal digestion, the precursors of such fats are split up into these two radicles. The See also:free fatty acid radicle then unites with an See also:alkali, and becomes transformed into a soluble See also:soap which is then readily absorbed in this fluid condition by the epithelial cells of the mucous membrane. There it is acted on by ferments (ii aces) and converted into neutral fat, which may remain in the cell as such. By the See also:reverse action on the part of the same ferments in the cell, these neutral fats may be redissolved and pass into the lacteals.

Many cells throughout the body contain this ferment. The soluble soaps which are probably conveyed by the blood will be quickly taken up by such cells, synthetized into neutral fats, and stored in a non-diffusible form till required. The fat in this condition is readily recognized by the usual microchemical and staining reactions. As fat is a food See also:

element essential to the carrying out of the vital energies of the cell, a certain amount of fatty See also:matter must be See also:present, in a form, however, unrecognizable by our present microchemical and staining methods. Some investigators hold that the soaps may become combined with See also:albumin, and that on becoming incorporated with the cytoplasm they can no longer be distinguished as fat. If from some cause the cell be damaged in such a way as to produce disintegration of the cytoplasm, there will be a breaking down of that See also:combination, so that the fat will be set free from the complex protein See also:molecule in which it was combined as a soap-albumin, and will become demonstrable by the usual methods as small droplets of oil. This splitting up of the fats previously combined with albumin in the cell by the action of natural ferments—lipases—and the setting free of the fats under the See also:influence of toxins represent the normal and the pathological process in the See also:production of so-called fatty degeneration. Calcification.—Calcification and calcareous deposits are extremely common in many pathological conditions. There are few of the connective tissues of the body which may not become affected with deposits of calcareous salts (fig. 47, Pl. V.). This condition is not so frequently seen in the more highly differentiated cells, but may follow See also:necrosis of secreting cells, as is found in the See also:kidney, in corrosive sublimate poisoning and in chronic nephritis.

These conditions are quite distinct from the normal process of ossification as is seen in See also:

bone. Many theories have been advanced to explain these processes, and recently the subject has received considerable See also:attention. The old See also:idea of the circulating blood being supersaturated with See also:lime salts which in some way had first become liberated from atrophying bones, and then deposited, to form calcified areas in different tissues will have to be given up, as there is no See also:evidence that this " metastatic " calcification ever takes place. In all See also:probability no excess of soluble lime salts in the blood or See also:lymph can ever be deposited in healthy living tissues At the present See also:day both experimental and histological investigations seem to indicate that in the process of calcification there is a combination of the organic substances present in degenerated tissues, or in tissues of See also:low vitality, with the lime salts of the body. From whatever cause the tissues become disorganized and undergo fatty degeneration, the fatty acids may become liberated and combine with the alkalies to form potash and soda soaps. The potash and soda is then gradually replaced by See also:calcium to form an insoluble calcium soap. The interaction between the soaps, the See also:phosphates and the See also:carbonates which are brought by the blood and lymph to the part results in the weaker fatty acids being re-placed by phosphoric and carbonic acid, and thus in the formation of highly insoluble calcium phosphate and carbonate deposits in the disorganized tissues. Pathological Pigmentation.—These pigmentary changes found in abnormal conditions are usually classified under (I) Albuminoid, (2) Haematogenous, (3) Extraneous. r. The normal animal See also:pigments and closely allied pigments are usually found in the skin, See also:hair, See also:eye, supra-renal glands, and in certain nerve cells. These represent the albuminoid See also:series, and are probably elaborated by the cells from albuminous substances through the influence of specific ferments, This pigment is usually intracellular, but may be found lying free in the intercellular substance, and is generally in the form of See also:fine granules of a yellowish-See also:brown or brown-See also:black See also:colour. In the, condition known as albinism there is a congenital deficiency or entire absence of pigment.

Trophic and See also:

nervous conditions sometimes cause localized deficiency of pigment which produces See also:white areas in the skin. Excessive pigmentation of tissue cells (fig. 48, Pl. V.) is seen in old See also:age, and usually in an See also:accompaniment of certain atrophic processes and functional disorders. Certain degenerative changes in the supra-renal glands may See also:lead to See also:Addison's disease, which is characterized by an excessive pigmentary condition of the skin and mucous membranes. This melanin pigment is found in certain See also:tumour growths, pigmented moles of the skin, and especially in melanatic sarcomata (fig. 49, Pl. V.) and cancer. The action of the See also:sun's rays stimulates the cells of the skin to increase the pigment as a See also:protection to the underlying tissues, e.g. summer See also:bronzing, " freckles," and the skin of the See also:negro. The coloured fats, or lipochromes, are found normally in some of the cells of the See also:internal organs, and under certain pathological conditions. This pigment is of a light yellow colour, and contains a fatty substance that reacts to the fat-staining reagents. Little is known regarding this class of pigment.

2. Haematogenous pigments are derived from the haemoglobin of the red blood corpuscles. These corpuscles may break down in the blood vessels, and their colouring material (haemoglobin) is set free in the serum. But their disintegration is more commonly brought about by " See also:

phagocytosis " on the part of the phagocytic cells in the different organs concerned with the See also:function of haemolysis, i.e. the liver, See also:spleen, haemolymph glands and other tissues. The 'haemoglobin may be transformed into haematoidin, a pigment that does not contain See also:iron, or into a pigment which does contain iron, haemosiderin. The haematoidin pigment may vary in colour from yellowish or See also:orange-red to a See also:ruby-red, and forms granular masses, rhombic prisms or acicular crystals. It can be formed independently of cell activity, nor does it require See also:oxygen. These crystals are extremely resistant to absorption, are found in old blood clots, and have been known to persist in old cerebral haemorrhages after many years. Haematoidin in normal metabolism is largely excreted by the liver in the form of bilirubin. Haemosiderin, an iron-containing pigment (probably an hydrated ferrous See also:oxide), is found in more or less loose combination with protein substances in an amorphous form as brownish or black granules. Cellular activity and oxygen appear to be essential for its development; it is found usually in the cells of certain organs, or it may be deposited in the intercellular tissues. Haemosiderin in the normal process of haemolysis is stored up in the cells of certain organs until required by the organism for the formation of fresh haemoglobin.

In diseases where haemolysis is extreme, particularly in pernicious anaemia, there are relatively large quantities occasionally as much as ten times the normal amount of haemosiderin deposited in the liver. In hepatogenous pigmentation (See also:

icterus or See also:jaundice) we have the iron-free pigment modified and transformed by the action of the liver cells into bile pigment (bilirubin). If the discharge of this pigment from the liver by the normal channels be prevented, as by obstruction of the See also:main bile ducts, the bile will accumulate until it regurgitates or is absorbed into the lymph and blood vessels, and is carried in a soluble state throughout the tissues, thus producing a general staining—an essential characteristic of jaundice. 3. In extraneous pigmentation we have coloured substances either in a solid or fluid state, gaining entrance into the organism and accumulating in certain tissues. The channels of entrance are usually by the See also:respiratory or the alimentary tract, also by the skin. Pneumonokoniosis is due to the inhalation of See also:minute particles of various substances—such as See also:coal, See also:stone, iron, See also:steel, &c. These See also:foreign particles See also:settle on the lining membranes, and, by the activity of certain cells (fig. 5o, Pl. V. and fig. 30, Pl. III.), are carried into the tissues, where they set up chronic irritation of a more or less serious nature according to the nature of the inhaled particles.

Certain metallic poisons give rise to pigmentation of the tissues, e.g. in the See also:

blue See also:line on the gums around the roots of the See also:teeth due to the formation of lead sulphide, or in chronic lead poisoning, where absorption may have taken place through the See also:digestive tract, or, in the See also:case of workers in lead and lead paints, through the skin. Prolonged ingestion of See also:arsenic may cause pigmentary changes in the skin. If See also:silver nitrate salts be administered for a See also:long See also:period as a medication, the skin that is exposed to light becomes of a bluish-See also:grey colour, which is extremely persistent. These soluble salts combine with the albumins in the body, and are deposited as minute granules of silver albuminate in the connective tissue of the skin papillae, serous membranes, the intima of See also:arteries and the kidney. This condition is known as argyria. Various coloured pigments may be deposited in the tissues through damaged skin See also:surface—See also:note, for example, the well-known practice of " See also:tattooing." Many workers following certain occupations show pigmented scars due to the penetration of See also:carbon and other pigments from superficial wounds caused by See also:gunpowder, explosions, &c. Hyaline.—This term has been applied to several of the trans-See also:parent homogeneous appearances found in pathological conditions. It is now commonly used to indicate the transparent homogeneous structureless swellings which are found affecting the smaller arteries and the capillaries. The delicate connective-tissue fibrillae of the inner coat of the arterioles are usually first and most affected. The fibrils of the See also:outer coat also show the change to a less extent, while the degeneration very rarely spreads to the See also:middle coat. This swelling of the walls may partly or completely occlude the lumen of the vessels. Hyaline degeneration is found in certain acute infective conditions; the toxins specially See also:act on these connective-tissue cell elements.

It also seems to be brought about by chronic toxaemias, e.g. in subacute and chronic See also:

Bright's disease, lead poisoning and other obscure conditions. The hyaline material, unlike the amyloid, does not give the metachromatic staining reactions with methylene-See also:violet or See also:iodine. The chemical constitution is not certain. The substance is very resistant to the action of chemical reagents, to digestion, and possibly belongs to the glyco-proteids. Amyloid.—The See also:wax-like or amyloid substance has a certain resemblance to the colloid, mucoid and hyaline. It has a See also:firm gelatinous consistence and wax-like lustre, and, microscopically, is found to be homogeneous and structureless, with a trans-lucency like that of ground-See also:glass. Watery See also:solution of iodine imparts to it a deep See also:mahogany-brown colour; iodine and sulphuric acid occasionally, but not always, an See also:azure-blue, methyl-violet, a brilliant See also:rose-See also:pink and methyl-See also:green gives a reaction very much like that of methyl-violet, but not so vivid. The reaction with iodine is seen best by See also:direct light; the reactions with the other substances are visible only by transmitted light. The name "amyloid " was applied to it by See also:Virchow on See also:account of the blue reaction which it gives occasionally with iodine and sulphuric acid, resembling that given with See also:vegetable See also:cellulose. It is now known to have nothing in common with vegetable cellulose, but is regarded as one of the many albuminoid substances existing in the body under pathological conditions. Virchow's conjecture as to the starchy nature of the substance was disproved by See also:Friedrich and See also:Kekule, who confirmed See also:Professor See also:Miller's previous finding as to its albuminous or protein nature. Oddi in 1844 isolated from the amyloid liver a substancecomposition C1sH2sNa2NSO17.

Krawkow in 1897 clearly demonstrated it to be a proteid in firm combination with chrondroitin-sulphuric acid. As probably the protein constituent varies in the different organs, one infers that this will account for the varying results got from the See also:

analysis of the substance obtained from different organs in such cases. This amyloid substance is slowly and imperfectly digested by See also:pepsin—digestion being more See also:complete with trypsin and by autolytic enzymes. There is no evidence that this material is brought by the circulating blood and infiltrates the tissues. It is believed rather that the condition is due to deleterious toxic substances which act for prolonged periods on the tissue elements and so alter their histon proteins that they combine in situ with other protein substances which are brought by the blood or lymph. Amyloid develops in various organs and tissues and is commonly associated with chronic phthisis, tubercular disease of bone and See also:joints, and syphilis (congenital and acquired). It is known to occur in See also:rheumatism, and has been described in connexion with a few other diseases. A number of interesting experiments, designed to test the relationship between the condition of suppuration and the production of amyloid, have been made of See also:late years. The animal most suitable for experimenting upon is the See also:fowl, but other animals have been found to react. Thus Krawkow and Nowak, employing the frequent subcutaneous injection of the usual See also:organ-isms of suppuration, have induced in the fowl the deposition within the tissues of a homogeneous substance giving the colour reactions of true amyloid. When hardened in spirit, however, the greater part of this experimental amyloid in the fowl vanishes, and the reactions are not forthcoming. They were unable to verify any direct connexion between its production and the organism of tubercle.

These observations have been verified in the See also:

rabbit, See also:mouse, fowl, See also:guinea-See also:pig and See also:cat by Davidsohn, occasionally in the See also:dog by Lubarsch; and confirmatory observations have also been made by See also:Czerny and Maximoff. Lubarsch succeeded in inducing it merely by the subcutaneous injection of See also:turpentine, which. produces its result, it is said, by exciting an See also:abscess. Nowak, however, found later that he could generate it where the turpentine failed to induce suppuration; he believes that it may arise quite apart from the influence of the organisms of suppuration, that it is not a biological product of the micro-organisms of disease, and also that it has nothing to do with emaciation. It is a retrogressive process producing characteristic changes in the fine connective-tissue fibrils. The change appears to begin in the fibrils which See also:lie between the circular muscle See also:fibres of the middle coat of the smaller arterioles and extends both backwards and forwards along the vessels. It spreads forwards, affecting the supporting fibres out-See also:side the epithelium of the capillaries, and then passes to the connective-tissue fibrils of the See also:veins. The secreting cells never show this change, although they may become atrophied or destroyed by the pressure and the disturbance of nutrition brought about by the swollen condition of the capillary walls. The circulation is little interfered with, although the walls of the vessels are much thickened by the amyloid material (fig. 51, Pl. V.). Amyloid Bodies.—These are See also:peculiar bodies which are found in the prostate, in the central nervous See also:system, in the lung, and in other localities, and which get their name from being very like starch-corpuscles, and from giving certain colour reactions closely resembling those of vegetable cellulose or even starch itself. They are minute structures having a See also:round or See also:oval shape, concentrically striated, and frequently showing a small See also:nucleus-like body or cavity in their centre.

Iodine gives usually a dark brown reaction, some-times a deep blue; iodine and sulphuric acid almost always See also:

call forth an intense deep blue reaction; and methyl-violet usually a brilliant pink, quite resembling that of true amyloid. They are probably a degeneration-product of cells. See also:Spurious Amyloid.—If a healthy See also:spinal See also:cord be hung up in spirit for a matter of six months or more, a glassy substance develops within it quite like true amyloid. It further resembles true amyloid which Schmiedeberg had previously obtained from cartilage and named " chondroitinic-sulphuric acid " (Chondroitinschwefelsaure). It also occurs in bones and elastic tissue, but is not present in the normal human liver. Oddi does not regard it as the essential constituent of amyloid, chiefly because the colour reactions are forthcoming in the residuum after the substance has been removed, while the substance itself does not give these reactions. Quite likely the amyloid may be a combination of the substance with a proteid. The soda combination of the acid as obtained from the nasal cartilage of pigs had the in giving all its colour reactions. The reaction with methyl-violet, however, differs from that with true amyloid in being evanescent.

End of Article: OTHER TISSUE

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