The softening of an organ, induced by in flatnmatory action, is frequently confined to one of the component tissues, especially to the cellular tissue ; the readiness with which the serous envelope may be stripped from off' a parenchymatous organ, depends more upon the subserous cellular tissue, than upon the other structures ; and, in like manner, the softness of a whole organ is often assignable, rather to the deficient tenacity of the mem brane which unites its lobules, than of the proper tissue.
Softening may be produced by causes totally differing frotn those produced by inflammation ; it may depend upon a deficiency- or perverted state of the blood, and an anmic state of the general system. For instance, in white softening of the brain, the arteries, which ought to have sufficiently nourished the af fected parts, fail to do so on account of their being blocked up, more or less, by abnormal deposits. In certain softened states of' the spleen, the blood contained in its parenchyma loses its consistence, and becomes more fluid than natural, from a perverted state of its constitution ; and the flabby muscles and general loss of tone of anmmic subjects are notorious.
In scrofula, the perverted state of the gene ral nutrition produces softening of peculiar tissues, for instance, of the bones ; and in the cancerous cachexia like effects occur.
Long continued functional inactivity, for in stance of the muscles of an extremity stricken with paralysis, tends to produce softening ; and pressure, in certain instances so interferes with the nutrition of a part as to diminish its cohesion. Fatty deposit in the ultimate cells of tissues and organs, renders them soft and flabby ; as will also infiltrations of certain morbid adventitious products. The com pound granule cells found in acute softening of the brain, and mixed with pus in other situations, are described in the article on AD VENTITIOUS PRODUCTS. Softening may be accompanied by atrophy, or by hypertrophy, which is generally produced by simple conges tion ; or no alteration of bulk may occur. Three degrees of softening are recognised :— in the first, the softened tissue is still solid, but it breaks down and tears and can be per forated with ease ; in the second, all solidity' is gone, nothing but a pultaceous semi-fluid mass is found ; and, in the third degree, the tissue is broken down and diffluent.
Softened parts may retain their natural colour, or may be paler, or may have an in crease of colour. Softening, without any change of tint, occurs in mucous and serous membranes, in the brain, heart, liver, and uterus. All post mortem softenings are of this kind, except where the colouring matter of the blood has tinted the effused fluids.
In certain softenings of the brain the af fected parts are much paler than usual, being of a dead white colour ; there is a diminution in the quantity of blood usually present in the diseased parts ; a like decrease of colour is found in other softenings.
Generally, however, softening is accom panied by reddening, or by an increased co lour ; the tints may vary from a bright ver milion to a brownish red, and may be seen as grey, almost black, and, occasionally, are yellow. These varieties of colour depend upon the amount of blood usually existing in the softened tissue, and upon the degree of congestion. The redness of softened tissues is occasionally partial, and merges into lighter tints as the tissue becomes harder. Partial effusions of blood, or highly injected vessels, are commonly found in red softenings.
Induration, generally speaking, is to be re garded as a symptom of previous or coexist ing diseased states ; its physical condition varies much in its nature, in the same or in different tissues, as proved by microscopical, mechanical, and chemical analysis ; and both observation and experiment tend to prove, that it is produced by causes of a very oppo site kind.
Changes in the amount of fluid destined for the nutrition of a part, frequently give rise to induration ; an increased quantity of blood and a consequent increased deposit of solid structure, produce simple induration of many organs, which are liable to variations in the quantity of blood they may contain, for in stance, the brain and spinal marrow, the cellular and muscular tissues ; also of denser structures, as bone, in which the induration is occasionally extreme, and in fibrous tissues ; they' produce also hardening of the lymphatic glands and of the salivary glands. The brain has been found to be increased to twice its natural density and consistence. Muscular, fibrous, and cellular tissues, become so hard, as to give out a grating sound when cut ; and the walls of some hollow organs, naturally soft and flaccid, acquire such a degree of firm ness, that they preserve, when empty, a glo bular or cylindrical form, and spring up with considerable force after sudden pressure ; and parts of bone acquire that degree of hard ness, which has been termed eburneoid indu ration. An increased quantity of the usual fluids of nutrition frequently gives rise to in duration, differing from that just described, in not being attended by deposition of solids. The accumulation of blood in the vessels of the lungs and spleen, the result of congestion, produces, sometimes, a great degree of hard ness and density of these organs. Diminution of the quantity of the same fluid, especially when there is also a compressing force, is also followed by an increase of consistence, and, generally, by a decrease in bulk of cer tain organs ; in pleurisy, for instance, dense false membranes, by their pressure, compress the lung into a small space, and its tissue be comes indurated from simple approximation ; for, on the removal of the compressing agents, the lung can be inflated.