128 MEDICAL JURISPRUDENCE Rigor mortis generally occurs, whilst the body is cooling. It is in no way connected with the nervous system, and it develops even in paralysed limbs, provided the paralysed muscle tissues have not suffered much in nutrition. It is retarded by perfusion with normal saline. Owing to the setting in of rigor mortis all the muscles of the body become'sttff, hard, opaque and contracted, but they do not alter the position of the body or limb. A joint rendered stiff and rigid after death, if flexed forcibly by mechanical violence, will remain supple and flaccid, but will not return to its original position after the force is withdrawn ; whereas a joint contracted during life in cases of hysteria or catalepsy will return to the same condition after the force is taken away. Rigor mortis first appears in the involuntary muscles, and then in the voluntary. In the heart it appears, as a rule, within an hour after death, and may be mistaken for hypertrophy, and its relaxation for dilatation, atrophy or degeneration. The left chambers are affected more than the right. Post-mortem delivery may occur owing to contraction of the uterine muscular fibres. In the voluntary muscles rigor mortis follows a definite course. It first occurs in the muscles of the eyelids, next in the muscles of the back of the neck and lower jaw, then in those of the front of the neck, face, chest and upper extremities, and lastly extends downwards to the muscles of the abdomen and lower extremities. It passes off in the same sequence. Time of Onset.—This varies greatly in different cases, but theua&erage period of its onset may be regarded as three to six hours _ after death in temperate climates, and it may take two to three hours" to develop; In India, it usually commences in one to two hours after death, and takes one to two" hours to develop. """^V Duration.—Intemperate regions, rigor mortis usually lasts for two to three days. In Northern India, the usual duration of rigor mortis is twenty- four to forty-eight hours in winter and eighteen to thirty-six hours in sum- mer. According to the investigations of Mackenzie 13 in Calcutta the average duration is nineteen hours and twelve minutes, the shortest period being three hours, and the longest forty hours. When rigor mortis sets in early it passes off quickly and vice versa. Cases 1C have occurred in which rigor mortis developed and disappeared within an hour and a half after death. In a case where death occurred from exhaustion after a prolonged illness of enteric fever, rigor mortis was evident everywhere on the body in three minutes and a half after djsath disappeared in a quarter of an hour and in less than an hour after death putrefaction had appeared in the limbs.17 Circumstances modifying the Onset and Duration of Rigor Mortis.— (a) Age.—Eigor mortis is said not to occur in the body of an immature foetus orless than seven months. A case ls is, however, recorded in which strongly marked rigor mortis was present in a five months' foetus. Rigor mortis is commonly found in the bodies of still-born infants at full term. Tarleton19 relates a case where rigor mortis was seen in a well-developed female child, which died during delivery. Cases of ante-natal rigor mortis, although rare, are recorded. This condition usually interferes with delivery. Dr. Jitendra Desai of Ahmedabad reported to me that in October 1938, he 15. Ind. Med. Gaz., June 1889, p. 167. 16. Bomb. Famine Hosp. Rep., 1901. 17 Savory, On Life and Death, p. 1%; Taylor, Princ. and Pract. of MecL. Juris., Ed. X, v ol. I, T>. 190. 18. Bomb. Famine Hosp. Rep., 1901. 19. Brit. Med. Jour., June 13, 1908, p. 1,424.