Another habit that is sometimes formed during this period of youth is the habit of drinking alcoholic liquors. Now, whatever we may think, whether we agree with those who say that alcoholic liquors are injurious, or whether we are of opinion with Dr. Parkes, that we are not in a position to say that alcoholic liquors are altogether injurious, we must agree with the statement that the drinking of alcoholic liquors is extremely pernicious to young people - there are no two opinions upon that point; and, perhaps, a still more important thing is, that habits of this nature are very easily contracted, but very difficult to get rid of later on in life.

While I am discussing habits, I may mention smoking - a habit that, in this country at any rate, is, practically speaking, confined to one sex. Now, whatever we may think with regard to smoking, whether we think it altogether injurious, or whether we agree with a large number of people who think that, later in life, after the fatigues of a day's mental and physical work, the soothing of a pipe or a cigar is a very pleasant and agreeable thing, and, on the whole advantageous, there are not two sides to the question when applied to growing people. Everybody agrees who has studied the subject at all, that for growing boys smoking is an unmixed evil, and that fact cannot be too widely known.

Consumption is the most fatal of all diseases during youth. I told you before that it is the plague of our climate, and it is especially so at this period of life. It is then it exerts the utmost fatal influence, and it is especially prevalent among young people who have to work either in trades where there is much dust in the air, or who have to work in close over-crowded rooms, where they breathe air over and over again. The trades in which consumption is especially prevalent are those in which there is much dust in the air, it does not matter what kind of dust; and there can be no doubt that a great deal of consumption among work-people would be prevented if they would take the precaution of wearing something to prevent the dust being drawn into the lungs. Several admirable things have been designed, and one of them has been designed by Professor Tyndall - a respirator, containing cotton-wool, which is capable of filtering off from the air that people breathe the dust that it contains, and there can be no manner of doubt whatever that if work-people could be induced to wear this, or something like it, they would be prevented, in many instances, from becoming consumptive. Many work-people are only persuaded with the greatest difficulty to use anything that prevents their trade from being a dangerous and therefore a lucrative one; and a most notable example of this is the extreme difficulty there was in introducing the Davy safety-lamp.

At this time of life, too, an‘mia, or bloodlessness, is particularly prevalent among those who work in overcrowded, close rooms, with many gas lights. It is especially prevalent among young girls who sit for a large number of hours together in such rooms, and the only cure for it is change of occupation; it is perfectly hopeless to do anything else.

Rheumatic fever is very prevalent among young people, from catching cold. This is a much more serious disease than is commonly thought, because it consists of inflammation of the fibrous tissues of the body, among which are the serous membranes of the joints, and among the serous membranes that are sometimes inflamed are the two that are inside and outside the heart - the endocardium and the pericardium; and when this happens it frequently causes a permanent alteration of the valves of the heart, so that those valves no longer act properly, and we have what is called valvular heart disease; this always gets worse, and cannot get better; it gets worse during the rest of life, and invariably shortens it, so that every possible precaution to prevent young people from getting rheumatic fever should be taken. It is not a communicable disease, like scarlet fever, whooping-cough, or measles, and has not the property of communicable diseases, that having had it once you cannot take it again; but, on the contrary, when you have had rheumatic fever once you are more likely to have it again, and if you do not get heart disease the first time you are very likely to get it the second time.

In manhood, the diseases we get are especially chronic diseases, and many of them result from having diseases in youth, for instance chronic rheumatism, and the most important thing during manhood is to take care not to eat too much food. In manhood, all that has to be replaced is the losses that are continually taking place; there is no increase in weight, we remain stationary at the same weight, or about the same, for some years; there are slight variations, but they are of no importance whatever; any great variation from the ordinary weight during manhood is to be regarded suspiciously; any great increase in weight shows that a man is either taking too much food or not enough exercise, or both; and it should be remembered, in connection with this, that in manhood a man should not leave off his exercise; he should take as much exercise as he finds, practically speaking, good for him, without tiring himself too much, or he will increase in weight, and begin to age sooner than he ought. On the other hand, any decrease in weight is to be regarded suspiciously, because it is likely to be the sign of some disease; nevertheless, the variation of a few pounds either way is of no importance whatever.