[13] Before I called attention to this form of headache in the last edition of my lectures, it had already been noticed without my knowledge, by a friend of mine, Dr. Blache, of Paris, in a very valuable essay on the headaches which occur during the period of growth. CHAPTER VII. THE DISORDERS AND DISEASES OF THE CHEST. In speaking of the ailments which occur during the first month after birth, I have already noticed the peculiarities of breathing in early infancy, and the difficulties that sometimes attend the complete filling of the air-cells of the lungs, and the readiness with which when once filled they become emptied of air and collapse. On this ground it is therefore needless for me again to enter, and I may pass at once to consider those ailments which rise in increasing importance from a simple cold or catarrh to inflammation of the air-tubes or bronchitis, inflammation of the lung substance, as pneumonia, and inflammation of the membrane which lines the chest and covers the lungs, or pleurisy. =Catarrh.=--A common cold or _catarrh_ is not one of the ailments of very early infancy. The watery eyes, the sneezing, the cough, the slight feverishness and the heavy head are scarcely met with until after the age of three months; nor, indeed, are they often seen till the child is old enough to run about, to go out for a walk, and to encounter in consequence all the variations of temperature and of damp or dryness inseparable from the English climate. This, however, is not entirely due to the greater exposure of the child to these influences as it grows older, but in part also to the fact that the lining of the air-tubes is less sensitive in early infancy than it afterwards becomes. The young babe if it catches cold gets _snuffles_, or stoppage of the nostrils, which first become dry, and then pour out an abundant discharge, which sometimes dries and forms crusts, and causes the child to suck with difficulty, and to breathe uncomfortably and with open mouth. In a few days, however, at the worst this discomfort passes away; and the only additional remark I have to make is, that since obstinate snuffles are sometimes a constitutional disease, the doctor's advice should always be sought if they last longer than a week. It is needless to describe a cold, but it is much more to the purpose to say how its occurrence is to be prevented, and nine times out of ten the observance of two simple rules will suffice for this. First, take care that there is no great difference between the temperature of the day and of the night nursery. The one should never be above 60 deg., nor the other below 50 deg., and the undressing and the bath should always take place in the warmer room. Second, never let the child wear the same shoes or boots in the house as it does out of doors. The change should be as much a matter of routine as the taking off its hat or its bonnet.