248 MICROBES, FERMENTS, AND MOULDS. 
bread. Spring-water, and still more river-water, as 
it is now supplied in towns by a system of pipes, 
is not free from organic matter, nor from microbes, 
although they are less abundant than in well-water. 
Purification is therefore necessary. 
With this object, it is recommended, especially in 
times of epidemic, to boil the water, so as to destroy 
the microbes contained in it. But this process expels 
the gases, and reduces the proportion of salts in solu- 
tion, thus rendering the water heavy and indigestible. 
It has, therefore, been suggested that only weak 
mineral waters should be drunk, such as that of 
Saint Galmier, which, if taken at the source and 
immediately placed in hermetically sealed bottles, 
contains very few microbes. But this process is 
costly, so that only rich people can avail themselves 
of it. The most practicable mode of purifying table- 
water and rendering it wholesome is by the use of 
filters. 
Ordinary Filters. Chamberland’s Microbe Filter. 
—Every one is acquainted with the common filter, 
made with crushed sandstone, charcoal, ete, which 
should be found in all households and kitchens. This 
generally suffices to free water from organic matter, 
and especially from the ova of ascarides (intestinal 
worms), which, when introduced into the system, 
develop and cause inconvenience to so many children, 
and even to grown persons. It is impossible to insist 
too strongly on the fact that the presence of ascarides 
