The belief in the special character of each of these diseases has received strong confirmation from the researches of the eminent Frenchman, M. Pasteur, and others who have followed in his track. They have discovered in the blood and other secretions, and in some of the tissues both of men and animals, minute microscopic organisms which differ in their characters in different diseases. Experiment has further shown that in some mysterious way these organisms are the cause of these diseases, for on inoculating animals with them the peculiar disease of which each was the accompaniment, and no other, was reproduced in the inoculated animal. As far as our knowledge goes at present then, we are forced to regard each of these as a separate disease, measles never passing into scarlatina, nor that into smallpox, but each, whether slight or severe, retaining throughout its distinct character. We have already seen how, in the course of various diseases, the pulse is quickened, and the temperature raised, constituting that state which we commonly call fever, but as the local ailment subsides the fever disappears. There is, apart from smallpox, measles, and the other so-called eruptive fevers, only one real essential fever commonly met with in childhood, and that is what the doctors call _typhoid fever_. The name, from the similarity of sound to _typhus_, from which, however, it is essentially different, has long been a name of terror in the nursery, and all sorts of epithets have been substituted for it, as gastric fever, and infantile remittent fever, and so on. Name it as you may, the fever is one and the same with the typhoid fever, which one hears of as prevailing constantly in many continental cities, and proving dangerous and fatal in any district almost in direct relation to the neglect of drainage and of proper sanitary precautions.