334 OF THE PRIMARY TISSUES OF THE HUMAN BODY. 



some diseases which powerfully affect the general vital energy, even though they 

 may not have been of long duration ; thus, after death from Typhus, the limbs 

 have been sometimes known to stiffen within fifteen or twenty minutes. The 

 same is observed in infants and in old people. On the other hand, where the 

 general energy has been retained up to a short period before death, the rigidity 

 is much later in coming on, and lasts longer; this happens, for example, in 

 many cases of Asphyxia and Poisoning, in which it has been said not to occur 

 at all. 



335. As the property of Tonicity manifests itself most decidedly in the non- 

 striated muscles in the living body, so do we find this post-mortem contraction 

 most remarkable in them. As soon as the muscular walls of the several cavi- 

 ties lose their irritability, they begin to contract firmly upon their contents, and 

 thus become stiff and firm, though they were previously flaccid. In this man- 

 ner, the ventricles of the Heart, which are the first parts to lose their irritability, 

 become rigid and contracted within an hour or two after death; and usually 

 remain in that state for ten or twelve hours, sometimes for twenty-four or 

 thirty-six, then again becoming relaxed and flaccid. This rigid contracted state 

 of the heart, in which the walls are thickened and the cavities diminished, was 

 formerly supposed to be a result of disease, and was termed concentric hyper- 

 trophy ; but it is now known, from the inquiries of Mr. Paget, to be the natural 

 condition of the organ, at the period when the " rigor mortis" occurs in it. 

 The contraction of the Arterial tubes is so great, as to produce for the time a 

 great diminution in their caliber; and this doubtless contributes to the passage 

 of the blood from the arterial into the venous system, which almost invariably 

 takes place within a few hours after death. The arteries then enlarge again, 

 and become quite flaccid, their tubes being emptied of their previous contents ; 

 and it was from this circumstance that the ancient Physiologists were led to 

 imagine that the arteries are not destined to carry blood, but air. So it has 

 been shown by Prof. Valentin, 1 that if a graduated tube be connected with a 

 portion of Intestine taken from a recently-killed animal, filled with water, and 

 tied at the opposite end, the water will rise in a few hours to a considerable 

 height in the tube, owing to the contraction of the intestinal walls. The post- 

 mortem contraction of the parturient uterus, to such an extent as to expel the 

 foetus of which the patient had died undelivered, is a phenomenon which has 

 been several times recorded; and Dr. Robert Lee has witnessed one remarkable 

 case, in which, the patient having died suddenly from the rupture of the uterus 

 and escape of the fostus into the abdominal cavity, the uterus was found, when 

 an examination was made twenty-four hours after death, to be completely in- 

 verted. 3 



7. Of the Nervous Tissue. 



336. We have, lastly, to consider the structure, composition, mode of growth 

 and regeneration, and special vital actions, of the Nervous tissue ; the one whose 

 existence is most distinctive of the Animal fabric, and which serves as the in- 

 strument of the operations that are most peculiar to it. Wherever a distinct 

 Nervous System can be made out (which has not yet been found possible in the 

 lowest of those beings, which, from their general structure and habits of life, 

 cannot but be ranked in the Animal Kingdom), it is found to consist of two 

 very different forms of structure ; the presence of both of which, therefore, is 

 essential to our idea of it as a whole. We observe, in the first place, that it is 



1 "Lehrbuch der Physiologic," band ii. p. 36. 



2 See Dr. Tyler Smith's "Parturition, and the Principles and Practice of Obstetrics," 

 p. 39, Am. Ed. The Author believes that Dr. T. Smith was the first to attribute this set 

 of phenomena to the cadaveric rigidity of the uterus. 



