472 THE POPULAR SCIENCE MONTHLY. 



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 solu- 

 tions and concentrations of the same are essential for certain ferments 

 or certain of their projjerties, and that they thrive weakly or not at 

 all in fluids otherwise constituted. A fluid may contain all the neces- 

 sary 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 differ- 

 ence 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 



