water, nevertheless fall easy victims to diseases which result from the rebundance or deficiency of the compounds which, in natural quantities, constitute the source of their daily life.” From the above comprehensive sketch of the principles of diet, we see to what an extent food influences the health of the individual, and consequently the prosperity and happiness of the nation. The subject of diet is so important, so full of interest, and opens so wide a field for interesting investigation, that I feel I cannot do better than refer those who wish for scientific information conveyed in popular terms on the subject of food, to Dr. Lankester’s “Lectures on Food;” and, in conclusion, I would say that it is only when the processes of digestion, respiration, and elimination, are in proper correlation, that we can expect either to enjoy or preserve good health. APPENDIX. A few brief observations on the control and prevention of infections diseases, such as small-pox, measles, scarlet fever, typhus fever, typhoid fever, cholera, &c. The above-mentioned diseases are capable of being transmitted from those who are infected to those who are not. It is at once cheering and obligatory to know that the spread of these infectious diseases depends upon certain specific conditions, and that these conditions are primarily within the control of man. This control and prevention of infectious diseases is one of the latest and greatest achievements of modern medicine. Small-pox is one of the most contagious diseases, but it is controlled by vaccination. Primary vaccination within certain limits, is a protection against small-pox, but it is a well ascertained fact that there is a period in the life of persons when the prophylactic or protective power of vaccinia dies out, or at the least becomes very feeble, consequently it is advisable for all who are in the proximity of those suffering from small-pox to be re-vaccinated, for the following reasons. Re-vaccination will almost without exception restore the protective power against small-pox: secondary vaccination is attended with no danger. The operation is so simple and the protection so certain and valuable. Scarlet fever and measles, though regarded as the inevitable diseases of childhood, and for which the mother is considered the best physician, and kitchen physic the best medicine, are simple in themselves, but on account of the sequelæ or diseases which generally follow, really require more attention in a sanitary point of view than they generally receive. Typhus, typhoid fevor, and cholera, are contagious diseases, and where the conditions of a locality are favourable they rapidly spread death and desolation around. Typhoid fever is generally caused by a specific miasm of sewers and neglected water closets, &c.