CHAPTER III.

TEXTURAL CHANGES.

WE now come to consider certain changes, to which most of the various organs of the body are liable, in a general way. These changes are essentially textural, and result from various disturbances of the normal degree and kind of nutrition. They are also for the most part slow and gradual in their course, and are thus termed chronic. They are intimately dependent on the condition of the blood, so that their consideration follows very properly on that of the diseases of this fluid.

Hypertrophy, as its etymology signifies, conveys the idea of increased nutrition and growth in the part affected. The term, however, is sometimes applied to parts which are simply enlarged, and it is essential to observe that this enlargement by no means necessarily constitutes hypertrophy, but may, instead, be attended with the opposite condition. This makes it necessary to distinguish real from apparent hypertrophy. In the former, the characteristic tissue of the part is enlarged, and more developed; if it be a muscle, the muscular fibres grow larger, and attain to greater energy of contraction, if it be a kidney, more renal tubes are formed with corresponding blood vessels. The size of the organ is not only increased, but its working power too; the muscle can raise a greater weight, and the kidney can produce more secretion. But if a liver or spleen be enlarged by ever so great a quantity of the peculiar matter termed "bacony," which is deposited interstitially between the elements of the tissue, their functional power is only thereby lessened, and deteriorated, for the simple reason that the new substance has pressed upon and caused wasting of the natural structure. It is, therefore, necessary in every case to ascertain what is the nature of the enlargement of a part before we pronounce it to be truly hypertrophied. Mere distension of a hollow organ, of course, is not hypertrophy; a huge emphysematous lung, or hydrocephalic brain are not really enlarged, but rather diminished in actual capacity. Great congestion of a part with blood may give it the appearance of being hypertrophied, but this again is only another kind of distension. Real hypertrophy requires a free supply of healthy blood, and is commonly attended with enlargement of the vessels of the part; this is not the case in apparent. The cause of real hypertrophy seems to be always the increased exertion of the organ, more than usual effort is demanded of it, and, according to the law of the circulation which we have noticed, more blood flows to the part than usual; this, if the organ be in a healthy state, not only supplies its waste, but furnishes material for increase and development. The heart

in various diseased states of its valves, the urinary bladder in stricture of the urethra, the remaining kidney when one has been destroyed, the muscles, and even the solid bones themselves, when long and actively exercised, afford excellent examples of true hypertrophy.

This process, though in several instances it brings about an abnormal state of the part, is yet for the most part not to be considered in the light of a disease. It is really a compensatory effort made by the system, to obviate as far as possible the evils that arise from some damage that an important part has sustained. Thus, if we find the walls of the heart greatly thickened, and its power proportionately increased, we should naturally fear that such an abnormal increase of power would prove a cause of danger to the system, and would probably induce hemorrhage in the brain, or elsewhere; but if we know that at the same time there exists regurgitant disease of the mitral or of the aortic valves, then, we see, that the hypertrophy, so far from being attended with danger, is useful and necessary to enable the circulation to be carried on against such impediments.

Atrophy is the opposite condition to hypertrophy; and is commonly conceived of as implying a wasting and diminution of the part. Atrophy, however, may have taken place to a great extent, without any diminution, but an increase of size. These are the instances of false hypertrophy, to which we have above alluded. In a few instances. atrophy is a natural process, as in the disappearance of the thymus gland when the age of early infancy is passed. Inactivity of a part, obstruction of its blood vessels, failure of its own vital energy, continued pressure upon its surface, are all recognized causes of atrophy. A muscle, if unused, becomes small and pale, and its tissue degenerates; the bones of a paralytic limb lose in density and strength, and in compactness of tissue; the brain in second childhood shrinks within its bony case, and leaves a space occupied by serum. Obstruction of the arterial branch leading to a part of the kidney will cause wasting of the epithelium of the tube in that part, ligature of the thyroideal arteries has caused considerable diminution of a goîtrous tumor. Thinning of the walls of the heart, renal degeneration, the fall of the hair, and the general decay of advanced age, are instances of atrophy from failing vital energy of the tissues. With the effect of pressure in producing atrophy, all are familiar; it is well exemplified in the absorption that takes place from the pressure of aneurism, which affects not only the soft parts, but the bones themselves. In most cases, atrophy is an actually morbid process, and is attended by a change in the condition of the elementary parts of the tissue which attests the unhealthy character of their nutrition. Atrophy often occurs as a secondary process, induced by some primary one, which may have been attended with apparent hypertrophy. Of this, the liver in the earlier and later stages of cirrhosis furnishes an instance.

Induration and softening, are terms that are commonly employed to express changes that have occurred in the consistence of various organs, rendering them more or less firm and dense than natural. They are, of course, very general in their meaning, and of themselves tell nothing as to the pathological condition of the part affected. This must depend

entirely on the causes of the changes in question. The commonest cause of induration is the effusion of fibrinous material into the interstices of a tissue; if this does not liquefy and become absorbed, it passes into the state of fibroid texture, and being blended with the elements of the part, it occasions a more or less considerable increase of density and toughness. Instances of this are extremely frequent in the lungs around tuberculous deposits, in the cirrhotic liver, and in the areolar tissue around ulcers. The tissues involved in the induration matter, as it is often called, are very apt to become atrophied, partly in consequence of their supply of blood being cut off by obliteration of the vessels distributed to them, partly from the effect of atrophic pressure itself. According to its seat, induration may be of trifling consequence, or very serious; in the general areolar tissue of the body, it may only cause slight impediment to the free movements of a part; in the valves of the heart it is a common cause of secondary disease, dropsy, and death. Textures are often rendered harder and firmer by other deposits than simple fibrinous, as by tuberculous, bacony, calcareous, but to these the term induration is not so strictly applicable.

Softening of a part may be brought about by very various causes. It is almost an invariable effect of acute inflammation actually existing; it is also found as the result of inflammation that has in great measure subsided; it occurs from deprivation of blood, as a kind of atrophy, and probably, in some cases, as a local result of a general cachexia. In all cases it involves a considerable deviation from the state of healthy nutrition, and if it proceeds far, may easily occasion a breaking down and destruction of the tissue. The distinction of various kinds of softening, especially of the red, or inflammatory, has often been considered difficult, but may generally be made with certainty by means of microscopical examination, which discovers in the former decided traces of exudation. Softening is connected with the hypinotic condition of the blood, and its subordinate crases, especially the typhous; induration, on the other hand, with the fibrinous crasis. Softening is more prone to occasion speedy destruction of textures and fatal disorder. Induration, to produce gradual changes whose effects are slowly and gradually manifested. Softening appears as a process of decay, and affects not only natural structures, but new formations, and even as we have seen tuberculous deposits and fibrinous coagula. Induration, on the contrary, though involving some degree of atrophy, tends to preserve the parts which it affects from entire dissolution.

Degenerations are changes of an essentially chronic nature, latent in their origin, and obscure in their progress, until they have produced such deteriorations of structure as give rise to prominent secondary phenomena. Those with which we are most acquainted are the fatty, fibrous, and calcareous. They are of extremely frequent occurrence, but their nature has scarcely been recognized until of late.

Fatty degeneration consists in the replacement of the healthy tissue of a part, by drops, or molecules of oily nature, which are deposited, as it seems, instead of the natural material. This character distinguishes it from fatty accumulation, which may take place to a great extent in the interstices of a tissue so as to overlay and conceal its ele

ments. In true fatty degeneration there is always destruction of tissue, which does not occur when there is merely an increase of oil in the substance of the part. A muscular fibre thus affected shows the sarcous elements, the real contractile tissue within the sarcolemma, replaced by glistening oil-particles, so that the functional power of the organ is pro tanto destroyed. The hepatic cells in true fatty degeneration not only fill themselves with oil, but fuse together with others, and break up into granulous films, entangling oil-drops; this destruction does not occur when they simply become loaded with oil from the presence of a large quantity of this substance in the food. The process by which fibrinous coagula, or extra-vascular deposits are broken down and dissolved, seems to be in some measure of the nature of fatty degeneration; there is commonly much free oily matter visible in the softened mass, and the exudation corpuscles seem to be thoroughly charged with it. Fatty degeneration is clearly a kind of atrophy, but not identical with the simple form; we have seen muscular fibres of the heart which were simply atrophied, and had lost their transverse striation entirely, which yet did not contain a single particle of oil. The prevalent opinion respecting the nature of fatty degeneration is, that there occurs a true conversion of the albuminous substance of the tissue into fatty matter, just as when adipocire is formed out of flesh immersed in water. We are rather inclined to believe that the change is effected in the way of an unhealthy nutrition, oil being deposited in the blood in the place of nitrogenized matter. However this may be, it is important to distinguish the following conditions in which the quantity of fatty matter in and upon a part is greatly increased. (1.) Mere accumulation of adipose substance in and around an organ, the tissue remaining healthy, (2.) Accumulation of adipose tissue in the same way, but with atrophy of the proper structure. (3.) Increase of oil in the elementary structure of a part without atrophy, or breaking up. (4.) True fatty degeneration, in which the structure is more or less destroyed, and its elementary parts converted into oily matter.

Fibrous Degeneration is somewhat allied to Induration, and is probably connected with the existence of a fibrinous crasis. It occasions the gradual thickening of serous membranes and of areolar tissue by the formation of an imperfect kind of fibrous structure. This may attain a considerable thickness, and then by its dead white aspect resemble very much a layer of cartilage. The capsule of the spleen is sometimes thus altered, and has been wrongly said to have undergone cartilaginification, for there is no real similarity between this substance and cartilage. The white patches formed on the surface of the pericardium and in the capsule of the liver, are produced in this manner, and so is also that thickening of the Glissonian sheaths, which give rise, in many cases, to cirrhosis. The fibres are probably formed, in part, directly out of the effused blastema, in part, also, by nuclei, developing short fibres, which unite, as Henle has described. This latter mode of formation is often observed in the spleen. The chief difference between induration and fibrous degeneration consists in this, that in the former, a notable quantity of blastema is effused, which becomes the induration matter, and compresses and atrophies the adjacent texture; in the latter, there seems to be scarce

any perceptible exudation, as it takes place slowly, and passes at once into the condition of fibre. Induration may affect any tissue, while fibrous degeneration is chiefly seen in membranes. Cartilage, however, is liable to a fibrous transformation of a somewhat different kind, which will be hereafter noticed.

The Calcareous degeneration rarely occurs as a primary change, it is almost always secondary to some other. Especially, it seems to be consequent upon a fatty degeneration of the arteries, to which the term atheroma is applied, and which may occur at any period of life, while the calcareous change is seldom observed very extensively except in advanced age. We have already alluded to the calcifying process, under the head of tubercle, as one of the metamorphoses which that deposit might undergo, and we shall find hereafter that it affects other formations also. It is often spoken of as ossification, and, indeed, not altogether without reason, as the "lacunæ" characteristic of bone are found in this substance also; they are, however, irregularly and imperfectly developed. The earthy matters deposited are principally phosphate of lime and magnesia, and carbonate of lime; Rokitansky considers that they are not so much new deposits as precipitations from their natural combinations with animal matters. Calcareous deposition seems generally to take place in parts whose vitality has been considerably lowered by previous morbid processes within them. Thus it is common, in lymphatic glands which have been the seat of scrofulous disease, in obsolete croupofibrinous deposits, in the coats of arteries which have begun to be affected by atheroma, and in the valves of the heart under similar circumstances. The atheromatous condition, which we shall describe more particularly when we speak of the diseases of arteries, may either terminate in softening and breaking down of the arterial coats, or in calcareous deposition; both of these changes often coexist, but the latter predominates in old age. We think, however, that deposition of earthy matter may take place to a great extent, so as to produce the ossification so common in the vessels of the aged, without previous atheromatous or fatty degeneration. The quantity of earthy matter in the bones becomes greatly increased in later life; it is even deposited in the so-named permanent cartilages, and it is, therefore, not surprising that it should also affect the walls of the vessels This degeneration probably is occasioned solely by a failure of assimilative nutritive power in the tissue itself.