49. In cases where the possibility of poisoning must be kept in view, and where matters may require to be procured for chemical analysis, it is essential to be sure that all instruments, vessels, and bladders used are scrupulously clean. 50. When any unusual odour is perceived, either in the blood in the course of making the dissection, or in the stomach when opened, it ought to be carefully observed, and if possible identified by all the medical men present. In this way alcohol, opium, prussic acid, oil of bitter almonds, and other odorous poisons may be recognised. The smell of the contents of the stomach ought always to be noted whenever it is opened, as the smell often alters rapidly. 51. The stomach and intestines should be taken out entire, and their contents emptied into separate bottles. If the stomach or part of the intestines present any remarkable appearance, examination may be reserved, if convenient, till a future opportunity; but in every circumstance it must be preserved and carried away, as it may itself be an important article for analysis. The throat and gullet may be examined at once, and preserved with their contents, which, if abundant, may be kept apart in a bottle. In addition to the alimentary canal and its various contents, portions of the solid organs of the body ought to be secured for analysis. The most important are the liver, spleen, and kidneys. A part of the liver, at least a fourth part, should be secured in every case of supposed poisoning; and in cases where the fatal illness has been of long duration, and therefore only traces of the poison may remain in the body, the whole of the liver, the spleen, and both kidneys should be secured. A portion of the blood, especially when the odour of any volatile poison is perceived, should be at once put into a bottle, closed by a good cork or stopper. 52. No person ought to undertake an analysis in a case of suspected poisoning unless he be either familiar with chemical researches, or have previously analysed with success a mixture of organic substances, containing a small proportion of the poison suspected. 53. All persons undertaking an analysis should bear in mind that the opinion of some other person practised in toxicological researches may be required; and they should therefore take care, when practicable, to use only a portion of the several articles preserved for analysis. The identity of the subjects for analysis must be secured by the rules in Sect. 13. VII. Examination in Cases of Suffocation