MARY CARMICHAEL.--The public has been completely fogged over the subject of tinned meats for years past. Some persons have tried to prove that tinned articles are better than fresh ones; whilst others have decided that all preserved foods are poisonous, and that those who partake of them do so at the risk of their lives. As is usual in such arguments, the truth lies somewhere between these extreme points, and we will endeavour to explain what are the various good and bad qualities of tinned foods. In the first place, we must notice that tinned eatables are very much better now than they were some years ago. This is particularly the case with the tinned fruits from California (the preparation of which is, we believe, entirely carried on by girls). For some years back we have been able to get tinned pears, peaches, apricots, etc., from California, and, as far as we can find out, no case of poisoning has occurred from their consumption. It may be said that all the tinned articles which are allowed to come into London are perfectly wholesome while they are fresh; it is only after they have been kept some time that they become injurious. Again, it must be remembered that tinned goods will not keep when once the tin has been opened. A large number of deaths have occurred from eating tinned meats which have been opened several days previously. It is of great importance to recognise what the poison in tinned meats is, and where it comes from. There is a popular notion, which is a very great fallacy, that the poison is derived from the tins, and that therefore there is no danger in meats preserved in jars or barrels. This is a great mistake, for although tinned goods do sometimes become contaminated with the metal of the tins, this is only very seldom the case. When the poison is derived from the tins, as it was in some cases of poisoning from tinned cherries, death is not very common. Whence comes the poison, of which we all read cases, of whole families being killed from partaking from a tin of salmon or sardines? It is developed in the food itself. This is not a case of organic matter going bad from decay. Articles sealed up in airtight tins will never undergo putrefaction. This development of poisons in tinned meats is a totally different phenomenon from putrefaction. It appears that if organic substances are kept for a long time, whether in the air or in airtight cases, extraordinary and little-understood changes occur in their composition, whereby, amongst other things, are developed definite chemical compounds known as "animal alkaloids." These are the poisonous agents in tinned goods. These alkaloids are allied, chemically, to strychnine, morphine, etc., but some of them are immeasurably more poisonous than any known vegetable or mineral production. A quantity of one of these alkaloids (occasionally found in tinned sardines), which is so small as to be almost impossible to demonstrate, has killed a whole family in twenty-four hours.