Signature Details.--Some of the details of the doctrine of signatures are amusing. For a considerable period nuts were supposed to be a good brain food, and some traces of this idea are still extant, although there does not seem to be any better reason for it than the fact that many nuts have an arrangement of their lobes which resembles the conformation of the brain. On the same principle the Chinese use ginseng-root as a general tonic. The extract is not {36} of any special significance in medicine, though it has come to be much advertised in recent years, and the Chinese continue to pay high prices for it. The reason is that the root of the ginseng plant often resembles the human body. The more nearly this resemblance can be traced, the more virtue there is for the Chinese in the particular specimen of ginseng. The signature is on the roots. It is good for man because it looks like man, just as the nuts are good for the brain because they look like the brain. In modern times we are likely to think that we are far away from any such self-deception. But our deceptions have a more appealing pseudo scientific element in them. Fish was for some time considered a good brain food because fish has phosphorus in it and so has the brain. The two reasons have as much connection as that between nuts and the brain; or ginseng and man. Astrological ideas came in to help out ignorance and foster supposed knowledge. The sun and the stars were favorable planets and the moon unfavorable. If anything about a plant reminded the gatherer of the sun or the stars, then that plant was sure to be beneficial, especially in chronic diseases. If anything reminded him of the moon, however, then it could be expected to be maleficent in influence. Though childish, this had yet its power to help. The use of nitrate of silver, which in the old days was called lunar caustic, because it had, in a fresh state, a silvery, moon-like sheen, was largely a matter of signatures. The signature went both by similitude and by contrary. Since the lunar caustic supposedly had a moon quantity, therefore it would be good for moon-struck people--the lunatics of the old time and of our own time. As a consequence nitrate of silver was used in many obscure nervous and mental diseases. In epilepsy it was commonly employed. Even in our own times, entirely on empiric grounds, it was used for such severe organic nervous diseases as locomotor ataxia and sometimes to such an extent as to produce argyria. Undoubtedly, its use, with confidence on the part of the physician and suggestion and persuasion on the part of the patient, did much to relieve sufferers from discouragement and from such psychic disturbance of their general health as would have made their condition seem worse.