476 THE POPULAR SCIENCE MONTHLY. 



As there are soils which are more easily nitrified than others, so 

 there are those which more readily bring forth disease than others ; 

 and it is the duty of hygiene to search further into the biological 

 processes going on in the ground. We are still very far from the 

 end : a boundless sea of probabilities lies before us ; but that need not 

 prevent our weighing anchor and spreading sail. 



Hitherto we have allowed ourselves to be guided in hygienic 

 practice and technics predominantly by the feelings, instincts, and 

 what we call common sense, and have only very recently begun to 

 establish our practice, which is, indeed, very primitive, on a scientific 

 and experimental footing. Dirt and impurity have till now been 

 somewhat indefinite conceptions. We use the terms whenever our 

 innate or cultivated sense of cleanliness is unpleasantly affected ; they 

 are generally called out by impressions on our sense of smell, taste, or 

 sight. What we call cleanliness plays an important part in daily life, 

 in a similar manner to that which conscience, the sense of right and 

 wrong, partly innate, partly inculcated, plays in our moral life. Just 

 as it can be regarded as a fact that conscientious men as a rule ac- 

 complish more and better than unconscientious, so cleanly men as a 

 rule are healthier and live longer than uncleanly men. As conscience 

 is more or less developed in different degrees of human civilization, 

 so also is the sense of cleanliness. Under the guidance of analogous 

 feelings, we have instinctively and empirically found out what it is 

 to our advantage to eat and drink, and how we should clothe our- 

 selves, before these subjects could be dealt with scientifically. 



Our established hygiene also was probably based in the first in- 

 stance chiefly on the suggestions of feeling. Those who are moving 

 in the new scientific direction should guard against considering all 

 that is not scientifically confirmed as wrong and unfounded, but they 

 should also not hesitate to subject established rules to a thorough 

 scientific and experimental criticism. This will necessarily teach us 

 that mere feeling has dictated much to us that rests upon false sup- 

 positions, and can either be omitted or must be changed. Practice 

 or technics always precedes science. Our branches of trade and in- 

 dustry also began on empiric roads, and were carried on in them for 

 thousands of years ; but how greatly have they been changed, im- 

 proved, and simplified, and how many new branches have arisen since 

 we began to apply the sciences of physics, chemistry, and mechanics 

 to them ! 



Hygiene, or the science of health, has a widely extended field of 

 labor in laying a scientific foundation for our sanitary regimen. Even 

 if in many cases it only shows that all is not as it has heretofore been 

 supposed to be, that has its great practical value. What harm did it 

 do to medical practice that the Vienna medical school in its day 

 showed up the errors of the then prevailing views, and radically as- 

 sailed the practice founded upon them which had been adopted for 



