Atrophy, wasting [tabes], consists in the withdrawal from a formation, after it has reached a certain grade of maturity and bulk, of its constituent elements, without any compensating regeneration of these; the result being decrease of substance, usually coupled with diminution of volume.

General atrophy attacks simultaneously, or in rapid succession, many organs and systems, if not all. Partial atrophy, one organ exclusively, or at least preferably. To the latter we shall at once direct our attention.

As with hypertrophy, so every organ is liable to become affected with atrophy.

Atrophy may, in the first place, be essentially primary, that is, developed in an organ as its first and sole anomaly, through influences more or less palpable, but external to such organ. Or, again, it may be secondary, that is, the result of previous textural alteration in the organ. The first is akin and analogous to the periodical intra- and extra-uterine processes of involution of certain formations, as also to the senile atrophy or marasmus of organs.

Primary partial atrophy is often, indeed, purely local; in not a few instances, however, it is probably conditional upon a general derangement of nutrition, of which, in such case, it is but the manifestation or symptom.

Causes of partial atrophy are:

1. Diminished Supply Of Blood

Diminished Supply Of Blood - of alimentary fluid - owing to compression, obturation, coarctation, or obliteration of the afferent bloodvessels; for example, partial atrophy with lobulation of the liver from adhesive phlebitis of branches of the portal vein, atrophy of the cartilaginous investments of the joints from sclerosis of the spongy condyles, and the like. Thickening of the minute and capillary vessels from within may co-operate with ossification of the great arteries in producing atrophy, especially in the brain, by rendering the walls of such vessels impermeable to the plasma of the blood.

2. Exhausting Disease

Exhausting Disease, or healing process; for example, atrophy of the bones and of their adjacent soft parts as a consequence of caries, of destructive suppuration in the effort to repair injuries; atrophy of the uterus after childbed, and exhausting puerperal diseases, etc.

3. Diminished Innervation

Diminished Innervation, paralysis, or impeded action of an organ owing to mischief of a mechanical nature; for example, atrophy of muscles in anchylosis, in luxations.

4. Pressure And Distension

These occasion increased absorption, a species of atrophy designated by the term detritus, usura. Even the most stubborn textures are not proof against it, the rigid osseous texture itself being in a high degree susceptible of it. It not unfrequently advances to the degree of a lesion of continuity.

5. Anomalies Affecting General Nutrition, And The Blood-Crasis In Particular

Upon such are based, for example, perhaps, the untimely decline (involution) of the generative organs in either, but especially in the male sex; but with more of certainty, several painful kinds of atrophy of the osseous system. Acute yellow atrophy of the liver is unquestionably founded upon an anomaly of the crasis, whilst the thyroid gland is atrophied by the fluids becoming impregnated with iodine.

6. Consecutive Atrophy

Consecutive Atrophy depends, as already stated, upon a previous alteration of texture, a breaking up thereof through hemorrhage (apoplexy), inflammation, and heterologous growths. Two contingencies may here arise; either the adventitious product and also the disabled textural elements of the organ may both undergo absorption, or else these latter may waste away alone, leaving in their place the new product, in the original or in subsequently diminished proportion and indefinite shape. Exemplifications occur in cell-infiltration of the medullary substance of the brain consequent upon encephalitis; in atrophy of the kidneys, resulting from inflammation or from Bright's granular disease; finally, in the merging of muscular fibre in the fatty degeneration of muscle and of normal textures in heterologous growths.

The morphological process connected with atrophy is not known in detail. To judge by a few facts - for example, the reduction of the uterus after delivery, the perishing of muscular fibre in fatty degeneration, the wasting of nerves, of lymphatic glands - the process essentially consists in the breaking down and liquefaction of the secondary elements (fibre), resulting from the metamorphosis of the cells and from the cells themselves. The nuclei at first remain, but subsequently undergo the same reduction and ultimate resorption. In the case of new growths, this blastema, arising out of the wreck of the said elementary bodies, may become subservient to the construction of anomalous textures.

With respect to the changes suffered by atrophied organs in their physical properties, we may offer the following general remarks.

The volume of the atrophied organ is indeed very commonly diminished, membranous formations having become thinner: this is, however, by no means invariably or immediately the case, at least not in any marked degree; for example, in atrophy of the lungs or of the bones. In hollow organs the volume may, owing to a coexistent passive dilatation, even become augmented. In such organs atrophy is conjoined either with normal capacity, simple atrophy; or else with dilatation of the cavity, so-called eccentrical atrophy - for example, of the heart, of the uterus, etc.; or, lastly, with coarctation, concentrical atrophy, in which the depth of the walls may be natural, or even greater than natural.

The weight of atrophied organs may be reduced, normal, or even increased: in the first case, proportionately to the simplicity of the atrophy; in the two latter cases the atrophy is consecutive, new growths supplanting the original textures.

The shape of atrophied organs embraces a variety of anomalies; amongst which we may specify the deformity which attaches to the con-centrical wasting of hollow organs and organs of cellular structure like the bones, the removal of the incisura interlobularis in atrophy of the lungs, the tuberous gland-like surface in secondary atrophy of the kidneys, etc.

The structure of atrophied organs involves various, and occasionally very marked changes. Thus, organs of cellular, of cavernous structure, by dint of the absorption which takes place at the parietes of their cells and canals, are rendered wide-celled - for example, in the lungs and in bones; and this structure eventually dwindles into a mere net or trellis-work. In consecutive atrophy, a new growth of a completely different texture occupies the place of the original structure; after inflammation, for instance, a honeycombed, meshy, or, on the contrary, a dense, callous, areolar tissue.

The consistence is in like manner subject to many changes. It is sometimes diminished, readily giving rise, upon slight occasion, to lesions of continuity; in the osseous system, for example. Sometimes it is increased. Secondary atrophy presents, in a marked degree, either contingency, according to the particular change of structure. Acute processes of the reduction of mass and volume determine, in certain organs, rather a decrease - chronic reduction rather an increase - of consistence.

Atrophied organs have a tendency to paleness of color. This, however, in some measure accords with certain changes affecting the native pigment of organs; for example, the decoloration of muscle, of the spleen to rust-brown, fawn-color, or yeast-color. The rule itself is, moreover, subject to sundry exceptions. Thus, the pure white of the medullary substance of the brain is exchanged for a whitish-brown. Organs that become atrophied without a proportionate thinning of their capillaries, sometimes, by dint of a relatively augmented supply of blood, assume a deeper color; for example, bones, kidneys. At the same time much depends upon the character of the atrophy; as in the cases of red and yellow atrophy of the liver.

The bloodvessels of atrophied organs become reduced in calibre, collapsed, and finally cut off from the atrophied organ, that is, the connection interrupted between its obliterated capillaries and the vascular trunk. This, however, has, in like manner, its exceptions, as in the case of dilatation of the trunk and ramifications of the pulmonary artery in atrophy and in emphysema of the lungs; in the case of dilatation of the bloodvessels of the brain, in atrophy of this organ.

The nerves of atrophied organs in all probability dwindle pari passu with the wasting of the diseased textures.

Atrophy is sometimes an acute, but more commonly a chronic process. In the former case it is frequently a painful affection.

The consequences of partial atrophy differ vastly in different organs. Either they are limited to a small range, to the locality itself, or they implicate more or less sensibly the entire organism. In this respect, atrophy of the central organs of the nervous system, and of the organs presiding over the preparation of the blood and over the grand secretory functions, namely, of the lungs, liver, and kidneys, is of course foremost in importance.

General atrophy in the form of emaciation, consumption, affects, indeed, the entire body, but by no means all organs and systems simultaneously or in an equal degree. Next in order to the falling off in the amount of blood, is that of the adipose, the areolar, and kindred tissues; then follows that of the voluntary muscles, then of the organic fleshy tunics and of parenchymatous organs, lastly of bones; whilst, even in the highest grades of the affection, the nervous system, so far as relates to its constituent elements, remains exempt. This order is, however, subject to many exceptions. The wasting of several formations low in the scale above laid down, occurs primitively, and offers the starting-point for the atrophy of the rest; for example, atrophy of bone.

The causes are loss of fluids of whatever kind, deficient reproduction of organic substance, fasting, various affections of the digestive organs, bodily and mental exertion, inordinate activity of the nervous system in various ways, excessive heterologous development, dyscrasis of the blood.

It is not rarely combined with the hypertrophy - for the most part, false hypertrophy - of internal organs, especially of the liver, spleen, and lymphatic glands.

A peculiar form of partial diminution is represented in the coarctation of canals and cavities. It is often, indeed, essentially a concentrical atrophy. It may, however, arise from external pressure, from deficiency of contents, from continued irritation of the sensitive parietes, or even from hypertrophy of, - or from various heterologous luxuriations and changes of texture implicating, - the said parietes. The highest grade manifests itself as morbid closure (atresia).