The most valuable applications of physiological tests have been in cases where narcotic poisons have been used, and especially in the early days of chemical analyses, when the methods then known were incapable of identifying these poisons. For example, in the year 1838 a woman was tried at Liverpool on a charge of having sent a poisoned pudding to another woman with the intention of poisoning her. The two children who were sent with the pudding tasted it on the way, and finding that it was bitter, mentioned the fact to the woman to whom they were taking it. She had other reasons for being suspicious, and, therefore, sent the pudding to a doctor to be examined. He applied various tests, but was unable to detect the presence of any poison, although from the taste he suspected that some narcotic poison was present. Accordingly, he gave a small portion of the pudding to a dog, with the result that the animal died within three hours with all the symptoms of poisoning produced by a narcotic poison. On the strength of this evidence, the prisoner was found guilty. A French poisoning trial which took place in the early part of last century is especially interesting from the fact that it is apparently the only recorded instance, prior to the recent notorious Crippen case, in which the deadly plant, henbane, was the original source of the poison. In the French case a child had been poisoned by some broth, and the symptoms had suggested the presence of a narcotic poison. The chemical analysis of alkaloidal poisons was at that time in its infancy, and in order to obtain proof of the poisonous character of the broth, some of the meat remaining in it was given to a cat. The animal died in about five hours, and the symptoms produced and the appearance of its body after death were all similar to those observed in the child. The evidence was therefore regarded as corroborative proof that the plant henbane had been introduced into the broth. In the present state of chemical analysis proof would have been expected of the presence of the active principles of henbane (hyoscine and hyoscyamine) in the broth and in the body of the victim, and physiological tests would probably only have been accepted as supplying additional proof of the identity of the poison. A striking example of the way in which the scientific evidence may succeed in establishing the innocence of a person accused of murder is seen in the following case, which was tried in 1835:--A woman, who had a violent disposition and was subject to attacks of hysteria, accused her husband of having attempted to poison her, and in proof of her charge produced a white powder, which, as she alleged, he had put into her food. The powder was found to be white arsenic, and the food on examination was found to contain a fatal quantity of that poison. The husband was therefore immediately arrested and kept in prison pending the investigation.