The loss of animal heat, though an invariable occurrence at some period after death, is not unfrequently noticed in disease. Every prac titioner must have met with it in hysterical cases; and it is a matter of notorious obser vation in cholera. On the other hand we have known the heat of the body not only continue but even return at a considerable period after death has unequivocally taken place ; a fact attributable either to chemical actions of a cadaveric description, or to the continuance of the processes which developed caloric during life. The mean time requisite for the com plete cooling of the body is fifteen or twenty hours; but the process is modified by a great variety of circumstances. It is slower after acute -than chronic maladies, but is very con siderably retarded in- asphyxial cases, except those occasioned by submersion.
Calorification is not the only function that may survive what is commonly called death ; thus the rectum and bladder have been known very frequently to discharge their contents after death ; and, which is still more remark able, parturition has taken place under such circumstances. The continuance of secretion, absorption, and nutrition has been argued from the exhalation of serous fluids in some parts, their disappearance in others, and the alleged growth of hair. Some of these facts are more rationally explained on such physical principles as are involved in transudation, endosmose, penetration, &c. &c.; as to the growth of hair, there is great reason to doubt the accuracy of the testimonies to the fact. Haller very justly observes that shrinking of the skin would produce an apparent elongation of the beard, which is the part upon which the observation alluded to has been most fre quently made.
2. The first alterations in the physical pro perties of the solids after death are softness and flexibility, to which succeed sooner or later the opposite conditions of firmness and rigi dity. The softness or want of elasticity may be owing partly to differences in the distri bution of the fluids in the tissues, and partly to changes in the tissue itself. The flattening of those parts upon which the weight of the body rests, the effect of deficient elasticity, is considered by Blumenbach a valuable cri terion of the reality of death. The flexibility of the joints obviously depends upon the re laxation of the muscles.
Rigidity is a change which has attracted great attention from its importance as an evi dence of death. Its period of accession de pends principally upon the nature of the ma lady. After long and exhausting illnesses, its appearance is early, but the duration is brief, and the intensity trifling. The same remark applies to the modifying influence of old age.
When the individual has been cut off by sud den accidental causes or by acute diseases, it comes on for the most part much later," lasts longer, and is more intense than in the former instances. It may appear within half
an hour after death or may be delayed twenty or thirty hours, according to the circumstances just mentioned. The mean duration is from twenty-four to thirty-six hours ; but it may last six or seven days according to Nysten, whose researches upon this subject are very valuable. We remember observing it once on the eighth day after death in the body of a criminal who had been executed by hanging, but are not aware at what time it had com menced. The parts which first present this chancre are the neck and trunk ; it then appears in ticie lovver extremities, and lastly in the upper. Its departure observes the same order.
It is yet to be proved that rigidity is not an invariable consequence of death. Nysten at tributes Thames assertion of its non-appear ance in some cases of asphyxia, to the lateness of its developement. If it could be wanting in any case, it would probably be so in sub jects attenuated and of flabby fibre. Louis in his Letters on the Certainty of the Signs of Death declares that he never found it absent even in the infirm and age-worn patients of Salpetriere, and Fodere gives a similar testimony to its universality.f The seat of rigidity is the muscular sub stance. , Of this we may be assured by the following facts. (1). It is observed in all those animals (including many of the invertebrata) which have a distinct muscular tissue. (2). Its intensity is in a direct ratio with the develope ment of this tissue. (3). It is destroyed by division of the muscles, a fact first noticed by Nysten4 (4). It remains when the cellular . membrane, skin, apoDeurosis, and ligaments are removed.§ (5). When very strong, it ren ders the muscles prominent as in voluntary contraction, or in that spasm which is inducec by rammollissement of the brain and spina marrow. Ch. Louis makes a remark of thi: kind in his admirable memoir upon some case: of sudden death.11 In hemiplegiac subjects rigidity is observe( to be no less strong in the paralysed limbs than in those which were unaffected by the disease. The temperature of the body has been said to influence it. Bedard* speaks of cooling as being always antecedent to rigidity, and Nysten has made a similar statement. But we have had many opportunities of disproving this observation. Ch. Louis noticed the pheno menon in some of the cues just adverted to, while the bodies were quite warm. Its occur rence in cold-blooded animals is, we think, a sufficient refutation of the idea that it bears any necessary relation with the loss of heat. Moreover Devergie has very properly pointed out the inconsistency of this notion with the fact that rigidity appears first upon the trunk, the region which is the last to be deserted by caloric.