No alteration of colour takes place in post mortem softening.
These distinctions of colour indicate no essential differences, as far as structure is concerned, for all coloured softenings may present the same histological characters. As a general rule, the red varieties are indicative of acute inflammation, yellow of subacute, and white or grey of deficient nutrition of the affected part ; but this rule is by no means invariable.
Universal softening of the brain, accom panied by a smell of sulphuretted hydrogen, is found in children suffering from general de bility, and occasionally in infants stricken with induration of the subcutaneous cellular tissue.
Softening from a defective state of the cir culatory apparatus is found, for the most part, in persons advanced in life, and consti tutes what is termed white softening. It de pends on the presence of osseous, cartila ginous, or atheromatous matter in the walls of the arteries, nearly or quite blocking up their entire caliber, and affecting vessels of all sizes. It may supervene upon occlusion of the common carotid from ligature, and, Indeed, upon any circumstance retarding or diminishing the quantity of blood to the brain ; intense inflammation may disorganise the ves sels, carrying blood to a remote portion of the brain, and thus cause softening ; or a severe blow, or the presence of a tumor of greater or less density and magnitude, may act in the same manner.
The very fact of adventitious products being found within the arteries, hints at a perverted state of the brain and system gene rally ; absorption does not progress in the diseased portions of the brain, which, having lost their supply of blood, are in a state ana logous to that of an extremity attacked with gangrena senilis.
The softening of the brain which is pro duced by post mortem agencies is of very frequent occurrence. It may exist alone, or may complicate the other varieties, and is caused by the decomposition natural to or ganised bodies after death, or by the infil trating action of fluids, which, either during life or in the agony of death, vvere effused into the ventricular cavities, and sub-arachnoid spaces.
Softening of the spinal cord is of not un common occurrence. It presents the same cha racters as those pertaining to the like affec tion of the brain, is produced by the same causes, and offers the same pathological cha racters. Softening of the whole cord may occur, but most frequently parts of it only are affected ; it is found softened most fre quently in the lumbar region, and not unfre quently in the cervical.
Induration of the brain may be general or partial, and presents three degrees of consist ence. In its first degree, the affected part is nearly of the consistence of a brain which has been left some time in dilute nitric acid; in the second degree, the indurated part is of a cheesy', and in the third of a waxy, fibro eartilliginons hardness. General induration affects either the whole or the greater part of the brain : the degree of hardness never exceeds the first variety. The induration is not al ways equal throughout the whole of the parts affected, the central medullary parts usually exhibiting a higher degree of it than the grey substance. A section of the indurated por tions generally presents increased vascularity, in the usual speckled and striated form ; yet the reverse is occasionally observed, the brain being preternaturally white.
Induration of the spinal cord may be general or partial. Billard found a spinal cord in a child of a few clays' old, which, without the membranes, supported a pound weight. In partial induration, the white, and not the grey, matter is usually affected. For further re marks on the softening and induration of the spinal cord, see the article NERvous CENTRES (Abnormal Anatomy).
Softening of the heart occurs as a diminished state of the cohesion of the muscular structure. It is a rare disease, and is produced by very opposite causes ; from inflammation, from a defective state of the nutrition of the organ, with or without general anthmia, and from a perverted state of the nutrition of the mus cular and cellular elements. The heart when softened collapses on itself when empty, tears with the greatest facility, and breaks down with little pressure, the finger perforating its substance and penetrating into its cavities with great ease. Its colour varies, being sometimes deep red and violet, at others dirty white, and occasionally of a faint y ellow hue. Soften ing of the heart may be general or partial, superficial or deep-seated ; it may be confined to the walls of a particular cavity, or to the ventricular septum, or it may occur in small patches, disseminated in the midst of the mus cular substance. Softening of the heart may coincide with hypertrophy of its walls, or a dilated state of its cavities, and Hope found it in a case of angina pectoris.