Allowing a few hours to elapse after apparent death, so that an equilibrium may be established between the carbonic acid in the air-chambers and the atmospheric air, if death is real the amount of this product exhaled from the anterior opening of the air-passages will exactly correspond with that transpiring from an equal area of the skin; but, if the slightest vital action continues, the proportion thus expired in a given time will far exceed the whole cutaneous transpiration. Collecting it at its point of exit, by a suitable contrivance, into a small transparent vessel containing clear lime-water, its merest presence, in contrast to any other reagent, will change this fluid at once, on shaking, into an opaque, milky solution.
The innervation test is rendered practicable through the inseparable connection of this attribute with muscular contraction; for, even if contractility is inherent in muscle, its excitation is possible only through the incorporation of nerve-elements. As this manifestation of nervo-muscular energy can always be sensibly excited by electrification during the persistence of the feeblest vitality, the utter failure to obtain such a result in parts the activity of which is essential to life, affords conclusive evidence of vital extinction. The respiratory arrangements of the glottis present a favorable opportunity for prosecuting this special mode of experiment. At every inspiration the contractions of the associated muscles stretch and separate the vocal chords, thus, nearly doubling the area of aperture. In expiration the muscles relax, allowing the parts by their elasticity to resume their natural collapsed appearance. These changes can be observed by placing the body before a bright light, and introducing a laryngoscope well back into the pharynx, so as to bring the superior laryngeal aperture into view. After death the rima glottidis presents the elongated narrow form, from the close approximation of its chords. If, under the repeated transmission of intense electric currents, properly directed, there is no responsive contraction so as to sensibly widen the aperture, death is certain.
The circulatory test, or the attempt to excite an actively congested state of the cutaneous capillaries, is preëminently the best, as it requires only simple and easily procurable appliances, which always yield decisive results either in the living or dead subject. The application of heat and the act of cupping are both effective topical means for perceptibly arousing this preternatural activity of the cutaneous circulation, even in the most languid condition of the system compatible with vitality. The entire absence of such distinctive physiological reactions and the occurrence of merely physical alterations, under the proper use of these respective measures, is undeniable proof of death. Over the heart is the most suitable region whereon to operate, as there the skin longest retains its vital warmth; but corroborative experiments may be performed over other parts of the trunk.
Hold the flame of a candle close to (but not in contact with) the