Besides these, there are a certain number of maladies that seem as if they must be due to the Bacteriaceæ, although a demonstration of the fact by the method of cultures and inoculation has not as yet been attempted. Among such, we may cite typhoid fever, diphtheria, murrain, tuberculosis (Fig. 4), malarial fever (Fig. 6), etc. As may be seen, the list is already a long one, and it tends every day to still further increase. All the progress that has been made in so few years in our knowledge of contagious or epidemic diseases is due exclusively to M. Pasteur and the scientific method that he introduced through his remarkable labors on fermentation. Now that we know our most formidable enemies, how shall we defend ourselves against them? As we have seen, bacteria exist everywhere, mixed with the dust that interferes with the transparency of the air and covers all objects; and they are likewise found in water. Under normal conditions, our body is closed to these organisms through the epidermis and epithelium, and, as has been shown by Mr. Pasteur, no bacteria are found in the blood and tissues of living animals. But let a rupture or wound occur, and bacteria will enter the body, and, when once the enemy is in place, it will be too late. One sole chance of safety remains to us, and that is that in the warfare that it is raging against our tissues the enemy may succumb. M. Pasteur has shown that the blood corpsucles sometimes engage in the contest against bacterides and come off victorious. In fact, chickens are proof against poisoning by charbon, because, owing to the high temperature of their blood, the bacterides are unable to extract oxygen from the corpuscles thereof. But, if the chickens be chilled, the conditions are changed, and they will die of charbon just as do cattle and sheep; but, as the result of the contest cannot always be foreseen, it is necessary at any cost to prevent bacterides from entering the body. [Illustration: I. Bacteria of charbon (_Bacillus antracis_.) II. The same cultivated in yeast. III. The _Micrococcus_ of chicken cholera. IV. The _Bacillus_ of tuberculosis. V. The _Spirillun_ of recurrent fever. VI. The _Bacillus_ of malaria.] Under ordinary circumstances a severe hygiene will suffice to preserve us; if a wound is received it should be washed with water mixed with antiseptics, such as phenic acid, borax, or salicylic acid. If water is impure, it must be boiled and then aerated before it is drunk. If the air is the vehicle of the germs of the disease, it will have to be filtered by means of a muslin curtain kept wet with a hygroscopic solution, glycerine for example. Finally, when, after an epidemic, contaminated apartments are to be occupied, the walls and floor and the clothing must be washed with antiseptic solutions whose nature will vary according to circumstances--steam charged with phenic acid, water mixed with a millionth part of sulphuric acid, boric acid, ozone, chlorine, etc.