DEATH. It is one of the fundamental doctrines of physiology, that every part of the organism has its own definite term of vitality, and that there is a continuous succession of the destruction of old cells and the formation of new ones in all tissues, and especially in those in which the most active vital changes are going on. as, for example, in the nervous and muscular tissues. Even the most solid portions of the animal frame, such as the bones and (to a less extent) the teeth, are undergoing a perpetual although a slower change of this nature; and throughout the whole body. there is a continuous removal of effete or wormout tissues, and a corresponding deposition of new matter. Every blow we strike, every thought we think, is accompanied by the death and disin tegration of a certain amount of mummlar or nervous tissue as its necessary condition ; and thus every action of our corporeal-life, from its beginning to its close, takes place at the expense of the vitality of a certain amount of organized structure. This is termed molecular D., and, within its proper limits, is obviously essential to the life and well being of the organism.
The cessation of the circulation and respiration may be regarded as constituting somatic D., or the D. of the entire organism, which must obviously be shortly followed by the molecular D. of every portion of the body.
We shall now briefly notice the principal modes in which D. occurs. D. happens either from the natural decay of the organism, as in old age, or (and .much more fre quently) from some of these derangements or lesions of the vital organs which occur in the course of the diseases and injuries to which we are liable. These derangements of the vital organs may occasion various modes of dying. Dr. Watson remarks in his Lectures en the Principles and Practice of Physic, that life rests on a tripod, whose three vital supports are the heart, the brain, and the Nags. Through the impaired functions of one or more of these organs, the tendency to D. is expressed. This is much the same as Bichat's statement, that " the mode of dying may begin at the head, the heart, or the lungs." The functions of these organs are, however, so mutually dependent upon each
other, that impairment in the functions of one of them may lead to D., while the mode of dying is chiefly expressed through the functions of another.
When a person loses blood to such an extent that he faints, if the flow of blood be not arrested, the state of fainting or syncope continues, and the heart's action ceases. The cause of D. here is, not that the heart is unable to contract, bat because its natural stimulus, the blood, does not enter it in sufficient quantity to excite contraction. This is termed D. by ancemia. In other cases, the stimulus from blood may be sufficient, but the heart may have lost its contractile power. Such a mode of death is said to be by asthenia (Gr. want of power). Many poisons and diseases, due to morbid materials in the blood (as, for example, cholera), prove fatal in this way.
D. may likewise be produced by suspension of the functions of respiration, as when access of the air to the. lungs is impeded, or when the actions of the muscles of res piration cease, in consequence of disease or injury of the brain or spinal cord. The tirst of those modes is known as suffocation or apnea, and we have examples of in drowning, smothering, choking, strangulation, etc. Forcible pressure upon the chest, such as sometimes happens in great crowds, or as occurs to workmen partially buried by the fall of earth, etc., will cause D. in a few minutes, if movement of the lungs is prevented by the pressure. Tetanus and the poison of strychnine prove fatal in this way.
D. by coma, or beginning at the brain, is caused by obstruction to the circulation through that organ by pressure (as, for example, when there is effused blood within the cranium, or when a portion of bone is depressed in a fractured skull); by clots of blood within the vessels; by various narcotic poisons, such as opium, alcohol in excessive quantity, carbonic acid, etc.