In view of the important function of the nose in warming, cleaning, and moistening the inspired air, the greatest care should be taken to teach children to breathe through the nostrils. When only a portion of the air enters through the mouth, the irritation is not as marked as when all the air is inhaled in this manner, but it nevertheless develops a condition of chronic irritation which is easily recognized by one familiar with its appearance, and which may lead to important complications. In many cases, mouth breathing is not due to habit, but to some obstruction in the nostrils or throat. These cases form a proper subject for the consideration of the physician. After the removal of any existing obstruction, children will sometimes, from force of habit, continue to breathe through the mouth, but this can usually be overcome by attention and firmness on the part of the parents. The prevention of grave throat diseases, such as diphtheria, necessarily forms a subject of much interest to the public in general and to mothers in particular. The causation of this disease has been much cleared up in later years, and we now know that the important factor is a bacillus--a small organism of the vegetable kingdom--which is the cause of this disease and a necessary material for its propagation. Bacteriologic investigations have shown that the so-called "membranous croup" is in by far the largest number of cases identical with diphtheria, and the same precautions which apply to the latter should therefore also be carried out in this disease. As diphtheria is strictly an infectious disease, and one which must be directly or indirectly contracted from a similar case, there is no sanitary reason why this dreaded malady in the course of time should not be entirely eliminated from the earth. In view of the fact that diphtheria is so frequently present in our larger cities, this may appear at present a Utopian idea. It is not so many years ago, however, when smallpox was almost universal, and yet we now but rarely have it in our midst. Not only is this the case, but the health authorities are severely criticised when a number of these cases exist, as indicating that there has been a lack of watchfulness in carrying out certain well-known means of prevention.