The cause of rigidity is referred by most authors to a sort of lingering vital contraction. It is often spoken' of as the last effort of life : " 11 semble que la vie " says Nysten, " se refugie en dernier lieu 'dans ces organes, et y determine le 'spasme qui constitue le roi deur." t This author not only refers it to con traction, but endeavours to explain how a very low degree of the ordinary kind of contraction may be sufficient to stiffen the muscles though not to move the part with which they are con nected. Supposing that a muscular effort equal to 20 would completely bend the elbow, one equal to 10 would semiflex it ; one equal to 5 would bend it a quarter of the distance ; while aforce equal to 1-20th only, would perhaps produce no motion at all, nothing but rigidity I Beclard alleges.three causes; the last contrac tion of muscular fibres, the general cooling of the body, and the coagulation of the fluids. The second of these we have already disposed of. Notwithstanding the high authorities in favour of ihe opinion that rigidity is caused by a vital contraction, we confess that to us it appears a very untenable position. All mus cular contraction in its normal condition alter nates with relaxation ; and although rigidity might be supposed to bear some analogy to the tonic spasm of tetanus, it differs widely from the latter in one important respect, that when overcome by violence it does not return. When we consider that the continuance of • the phenomenon in question is long after the cessation of any vital action; that the ; usual time of its accession is precisely that - which we have every reason to consider *the r most unfavourable for the occurrence of any l vital action, viz. when all animal heat is tinct, and when sanguineous congestions in the 3 depending parts of the body prove the capil s laries to have lost their contractility; it is cult to regard the process as of a vital 1 racter. The mere fact that the rigidity comes on and remains. long after the muscles have ceased to respond to the stimulus of galvanism, reduces the hypothesis to the last degree of improbability. Moreover we should scarcely expect the last act of life to be performed in the extremities ; we should. naturally look for it about the trunk, in conformity with the order of disappearance observed by all other vital actions ; but as we have stated above, this phe nomenon both appears and declines first upon the trunk ; in other words, according to the hypothesis, the muscles in this part expire while those of the extremities are still alive. Devergie is puzzled to reconcile the long continuance and intensity of rigidity in cases of asphyxia from carbonic acid, with the fact that this agent is destructive to contrac tility. NVe are somewhat surprised that he was not brought, by the mutual opposition of these facts, to consider that rigidity and vital contraction have nothing in common but the tissue in which they are manifested.
The third cause enumerated by Beclard is the coagulation of the blood. This is probably nearer the truth than are the other explanations of the plienoinenon ; but it would be more correct to say that rigidity and coagulation of the blood are effects of the Ktme causes, viz. coagulation of fibrin. They occur about the same time, and are impeded by the same agents. It has been proved that the muscles are the subjects of the rigidity, that they are contracted, and that their contraction is not of a vital nature. As this change must there fore be either mechanical or chemical, what rnore probable cause (in the absence of actual demonstration) can be imagined than the coa gulation of fibrin in the muscles? The rigidity occasioned by certain diseases may be mistaken by an unpractised observer for mortal stiffness. This error is most likely to be committed in cases of hysteria, for this affection, not content with imitating almost every other malady, has been often successful in mimicking death itself. Tetanus is in
stanced by some authors as a disease likely to occasion mistakes of the kind alluded to. This may be true of hysteric tetanus, but not of the idiopathic or of the traumatic species, which have characters too striking to be overlooked by even the most inexperienced. Besides, if the rigidity of any given case, supposed by one to be cadaveric, were by another proved to be tetanic, we are of opinion that the condition of the subject would be not a whit less hopeless, since the case implies that the respiration and circulation are apparently extinct; and when this is the case in tetanus, we may feel quite certain that if the patient is not actually dead, he is quite irrecoverable. Nysten de clares that the rigid spasm of disease may be always distinguished from that of death by the circumstance that it precedes the loss of heat in the former case, while in the latter the order of the events is just the reverse. This test holds good in a very large proportion of cases, but must not be implicitly relied upon, because, as we have before observed, corpses not unfi-equently retain their caloric for some time after rigidity has commenced. A better criterion is that of overcoming the rigidity by force; if it be cadaveric, the contraction is completely annihilated ; if morbid, it will return when the force is withdrawn.
A species of rigidity more likely to be con founded with the cadaveric is that which is soinetimes found in the dead body, but which is the product of disease. Of this description is the spasmodic contraction which often con tinues after death by apoplexy and other cere bral and spinal diseases ; and the observation of which is as old as the time of Ilippocrates. M. Marc relates the case of a gentleman who went to a theatre apparently in good health, and after the representation was over, was found by his friends sitting in the front of the box, with his head resting upon his hands and his elbows on the ledge. He had died of'apo plexy, and been retained in that position by the tonic spasm of his muscles.'f' This con tra.ction is unquestionably vital, but it ceases after a. few hours, and the flexibility is then succeeded by true cadaveric rigidity. In medico-legal cases it is of the utmost moment to bear this distinction in mind, but it is one that has received much- too little attention. Many of the standard works upon forensic medicine are altogether silent upon the subject. Its importance was proved by a case which occurred in France some years ago. The body of a man named Courbon was found in a ditch, with the trunk and limbs in such a relative position as could only have been maintained by the stiffness of the articulations. This stiffness, moreover, must have come on at the very time when the body took the said position, unless it could be imagined that the body had been supported by the alleged mur derers until the joints were locked by cada veric stiffness, a supposition infinitely too im probable to be entertained for an instant. But by regarding the rigidity as of a. spasmodic nature (resulting from apoplexy, of which there were sufficient proofs in the necroscopy), the difficulties of the case were altogether removed. A full report of the case, and of the medico legal consultation upon it, will be found in the seventh volume of the Annales d' Hygiene. In death by asphyxia there is often a spasmodic contraction which may continue for some time after decease. Orfilat is of opinion that this may be readily distinguished by the continu ance of animal heat, which he agrees with Nysten in judging to be incompatible with rigidity. While denying the universality of this principle, we think it sufficiently extensive to admit of a very useful application in a great number of instances.