IN AIR, WATER, AND FOOD. 



many practical difficulties, and any one entering upon 

 it should perform, in the first instance, a great many 

 preliminary experiments in order to determine the 

 most convenient and most delicate methods of 

 examination. 



Many disease germs will retain their vitality in 

 water, and there can .be no doubt that many are 

 introduced into the organism in this medium only. 

 From the evidence that has been adduced, it is certain 

 that both typhoid fever and cholera are disseminated 

 by drinking water, and almost as certain that if pure 

 wholesome water had been supplied to the victims 

 instead of the disease-carrying fluid, many lives would 

 have been saved. That some disease germs will live 

 for a considerable time in water, may be proved by 

 experiment. Pus-corpuscles from the bladder may 

 be kept alive in water, to which a very little albumen 

 or serum has been added. The gonorrhoeal poison- 

 germ, as well as the bioplast capable of producing 

 purulent ophthalmia, will also retain their vitality in 

 water, and probably even in water containing soap 

 and other things dissolved in it. Much of the water 

 containing disease-producing germs is very rich in 

 organic matter, and the products of the decomposition 

 of organic matter. Hence it is always desirable to 

 discard such water for drinking or culinary purposes. 

 Although there can be no doubt that many bad 

 specimens of water are perfectly harmless, as we are 

 unable to say whether disease germs are actually 



