Schjerning[721] considers blisters containing highly albuminous serum as diagnostic of burns produced during life. In some conditions of depression of nutrition blisters occasionally form, but are not liable to be confounded with those caused by burning.
A second anatomical feature of much importance, even more so than vesication, is the condition of the skin to which the heat was applied. It assumes a dusky red color and a dry and parchment-like condition (Case 8). Surrounding this is an area of grayish-white skin bounded by a sharply defined and deeply injected red line, which in turn shades into the color of the surrounding skin. These features are more or less pronounced according to the degree of heat applied and to the length of time of contact; or, in other words, to the depth and severity of the burn (Plate I.).
MEANS OF DISTINGUISHING ANTE-MORTEM FROM POST-MORTEM BURNS.
Differentially, a distinction is to be made between the surrounding redness and the line of redness. The redness due to capillary distention is transient, disappears under pressure during life, and fades after death. The line of redness is permanent, changing but little under pressure, and remains after death. It is a vital reactionary effort, a true line of separation between living and dead tissue, formed in the same manner as the line of demarcation in sphacelus or gangrene. This line of redness, developed only during life and permanent after death, is of great significance in cases with a medico-legal bearing. It has been already stated that in persons in a condition of depressed vitality the appearance of redness and vesication is sometimes very tardy and imperfect, and that death from shock or pain may occur before their development at all. They are vital processes and require time for their appearance in proportion to the activity of the powers of reaction. Hence in cases of burning resulting fatally where vesication and redness do not appear, the circumstances must be carefully considered before deciding that the burns produced were post mortem. With these qualifications, it may be stated that the presence of the red line is almost uniform in burns inflicted during life and absent in those occurring after death.
If upon a body bearing evidences of exposure to heat there be found blisters containing highly albuminous serum, and such blisters, after the removal of the cuticle, present a bright red base surrounded by a bright and sharp line of demarcation, with redness of adjacent surface, we are justified in concluding that the burns were inflicted ante mortem or, at farthest, within a few moments of death. If, on the contrary, the red line is absent and the blisters contain a thin watery fluid, with a yellowish and dry condition of their base after removal of the cuticle, the presumption is that the burning occurred post mortem.
Where a number of burns are found upon a body, the question whether they were produced simultaneously may be raised. This can be answered by examination as to their condition. If some show signs of recent infliction, while others are in conditions of suppuration or other changes which only occur after an interval, a difference of time in production would be probable. But if all present mainly the same conditions, the probability of their occurring at the same time may be concluded (Plates I. and II.).
The Condition of the Blood.—Special examination of the blood of persons dying from the effect of burns has been made by competent observers. While it is not at present possible to define an exact and constant condition, specially characteristic, some features of interest have been recently recorded.
The color of the blood has been variously reported; in some cases as being of a dark color and in others of a bright arterial hue. Death by asphyxia or suffocation, by the deprivation of oxygen, and by the products of combustion, would be accompanied by a dark or venous hue of the blood. An atmosphere containing an excess of carbon monoxide, resulting from combustion, would cause death by apnœa with an arterial hue to the blood.[722] But other influences must be considered. According to Schjerning,[723] it is difficult to deduce positive conclusions from the condition of the blood. The changes induced by the spleen and kidneys, as well as the varying intensity of the degree of heat to which the body may be subjected, tend to render positive and constant conclusions from this source difficult.
Falk[724] refers to the bright red color of the blood found in some cases, and explains this condition in part by the influence of chemical changes in the tissues surrounding the vessels.
Wertheim[725] describes certain conditions observed by him and mentions an increase in the number of the leucocytes, together with the presence of hæmoglobin and melanin.