The post-mortem appearances, however, except in a few instances, are not very characteristic; nevertheless they may be of great _negative_ value in proving that a certain poison has not been administered, or that the patient died from the effects of disease. Two symptoms, excessive lividity of the body and early putrefaction, formerly supposed to indicate death by poison, are now known to frequently follow other modes of death. It may nevertheless be remarked, that the appearances after death which may be produced by poisons are, in one great class, the signs of inflammation of the alimentary canal; in another, the signs of congestion of the nervous system; and in a third, a combination of the two. The detection of poison in some of the food which has been left untaken or in the matters vomited would seem to be conclusive evidence of the administration of poison; but it is to be recollected that designing persons have mixed noxious materials with food or rejected matters, in order to feign poisoning, or to cast unjust imputations upon others. When called to a case of supposed poisoning during life the practitioner’s duty is two-fold. His first aim must of course be to preserve life (see next chapter); his second, to forward the interests of justice. But if he reaches the spot too late to save life his duties are undivided, for he has but to see that justice is done, and in order that there be no failure it is important that all his observations be committed as speedily as possible to writing. He should inquire the time at which any substance was last taken, the nature of the symptoms, the hour at which they commenced, and the precise time at which death occurred. He must take possession of any food, medicine, vomited matters, urine, or fæces which may be in the room; and if possible he is to seal them up, in new and clean vessels, duly labelled, for examination. Then the position and temperature of the body are to be observed, the appearance of the countenance, the presence or absence of rigor mortis, with the nature and warmth of the apartment, the situation of any marks of violence, and the condition of the inside of the mouth and gullet. In addition to the ordinary rules to be observed in conducting post-mortem examinations in cases of suspected poisoning, something more must be done with a view to preserving portions of the body for subsequent examination. The alimentary canal is the most important organ to be thus secured, and it should be removed in separate portions. A double ligature should be passed round the œsophagus in the chest, and the duodenum a few inches below the pylorus should be secured in like manner; by cutting across the gullet and gut between these ligatures, the stomach may be removed without any danger of spilling its contents. It is best to open the stomach after it has been introduced into the receptacle prepared for it, so that its pathological condition may be noted as early as possible.