INTRODUCTION OF DISEASE GERMS 

 INTO THE BODY AND OF THEIR ESCAPE. 



Disease Germs in Air, Water, and Food. Such 

 minute particles as those described in the last section 

 are liable to be suspended in the air we breathe, or 

 they may be disseminated through the water we 

 drink, or hidden in the food we eat. Not only so, but 

 there is reason to think that some kinds of these 

 contagious disease germs even grow and multiply 

 outside the body. Indeed, it appears probable that 

 a few actually acquire their virulent properties after 

 they have left the organism in which they have been 

 developed, while they remain immersed in some 

 extraneous medium containing the proper elements 

 for their nutrition and further development. 



That such particles as those represented are 

 sufficiently light to be supported in the air and 

 carried long distances by air currents, is proved by 

 the fact that the scales of the wings of insects and 

 starch corpuscles, each of which weighs more than a 

 hundred times as much, are supported by the slight 

 currents of air in our ordinary rooms, deposited upon 

 shelves, and even transported long distances. The 

 careful examination of the particles suspended in the 

 air as seen in a sunbeam, renders all further remarks 

 upon this part of the question superfluous. 



