decomposition, and even if fluid, from infiltration in an œdematous or dependent part, this is always serum, unlike the vital fibrino-albuminous solution coagulable by heat. The pathognomonic distinction, however, is the difference presented by the underlying cutis on removing the loosely adherent cuticle. This, after death, has an unalterable yellowish-white, crisp, horny appearance, in obvious contrast to the efflorescence of vital active congestion, which can be repeatedly displaced and renewed by recurrent pressure.
Although circulation is a vital necessity, the chemical products of its activity would of themselves speedily destroy life except for the concurrent exercise of the respiratory and other functions.
Tissues, such as the nervo-muscular, which perform some specific action, may be classed as active in contrast to passive, such as the osseo-fibrous, which merely subserve some mechanical office. When the ultimate particles of passive tissues are fully developed, they remain in that state for a longer or shorter period, and then gradually decay. Active tissues, during their development, appropriate a store of energy which, at maturity, they are capable of instantly expending in the manifestation of their special powers. Such exertions are inevitably attended by degradative transformations of their material elements. Cardiac movements and their associated vital coördinations involve the expenditure of nervo-muscular energy, and consequent production of simpler compounds, such as carbonic acid, the undue retention of which in the blood would cause certain death. Such a fatal contingency is prevented by the circulatory forces propelling the carbonized blood into the pulmonary capillaries, where an interchange with the oxygen of the air takes place through the intervening membrane till the vesicles become surcharged with carbonic acid, which is then expelled by the expiratory forces through the anterior openings of the air-passages, where its detention is evidence of vitality, while its utter absence under adequate tests is undeniable proof of the opposite condition. For, though certain cold-blooded animals can exhale a sufficient quantity of this product through their skin to permit a reduced vitality, in man such a cutaneous transpiration is exceedingly minute and altogether inadequate to the maintenance of life, and it may continue even after death as a merely physical property of tissue.
Innervation is blended with and controls all the vital operations, being conspicuously implicated with muscular contraction, an act primarily concerned in the various movements of respiration and circulation. The frequently-repeated transmission of intense electric currents is the most powerful stimulus of contractility, and, when such a measure fails to excite contraction in muscles essential to life, death must have occurred.
"When rigidity and putrefaction are actually established, they may be accepted as infallible post-mortem indications. The former state arises from the muscles and other soft tissues becoming so stiffened as
