we may have another hygienist who shall make as beneficial a use of them as the surgeon Lister has made of the investigations of Pasteur and others in his antiseptic bandage. The mycologist did not deduce the ultimate practical results—that belonged to the surgeon; and on this ground I believe that the hygienist is not yet a superfluous piece of furniture.
The mycologists have told us, for example, that particular solutions and concentrations of the same are essential for certain ferments or certain of their properties, and that they thrive weakly or not at all in fluids otherwise constituted. A fluid may contain all the necessary constituents, but be too diluted or too concentrated. We may consider all putrefaction and decay of suitable substances, the refuse of our households, the waste water with which we irrigate and manure the soil, as affording food-fluids for the lower organisms. Then we might think—and the like has been thought and said—that dirt is not dangerous to health if it is only properly concentrated. It has been asserted that there is much more dirt in the country and in the villages where citizens go—as they say—to get the air, than in the city. A closer investigation would, however, show that there is a real difference between the city and the village, between country life and city life, but not between the consequences of filth in the city and in the country. Cleanly kept houses are healthier than dirty ones, even in the country. The villages, however, are only apparently filthier than the cities. Indeed, the great density of the population of the cities is in itself like a concentration of the filth, and the scattering of the dwellings in the country is like a dilution of it. In the villages the manure-heaps are on top of the ground and open to the air, which, ventilating them freely, effects a salutary dilution and change: in the cities we do not bring the dirt out into the yard, but we deposit it by the walls of our houses; we do not let the free atmosphere work upon it, but try to keep it away from the air as much as possible by inclosing it in pits which are well covered and arched over, but are connected with the house by invisible pipes and canals. We let nothing escape into the free air, but believe that we Heed not regard what reaches the ground under the house and the air within the house. In the cities we insist very much on outward cleanliness, that the dirt must not be exposed, and cover it up beautifully in our houses and yards, so as to make the impression that there is none, as a dirty skin and foul linen may be covered by handsome outer garments.
Admitting that there may be a kind or amount of concentration of filth in the soil that will prevent the growth of certain ferments, as the development of fermenting bacteria and fungoids is prevented in fruits by seething them in concentrated sirups, hygiene has yet to ascertain how highly concentrated filth in the soil must be to prevent the ferments in it that contribute to cholera and typhus from being effective. It should also be borne in mind that even if a sufficiently