SANITARY NOTES ON POTABLE WATER. 
561 
Beyond the general interest of the question I had another 
object in view when I gave my attention to the bearing 
of putrid matter upon the virus of zymotic diseases. 
In two consecutive papers, which were read before the 
Royal Society,* I have endeavoured to ascertain the com¬ 
parative and absolute value of certain purifying media of 
water by what I may call a physiological test, that is to say, 
by the action of the filtered water upon certain organic matter. 
Supposing a water contains bacteria, or in fact any agencies 
which are capable of inducing fermentation. Supposing 
further that such filtered water, whilst all infecting atmo¬ 
spheric influences are excluded, be brought in contact with 
fresh meat, the smell of the latter must after a time indicate 
the presence or absence of such putrefactive agents. 
As I then found in the course of these experiments that 
meat in contact with water which had been purified in a 
certain way remained fresh for weeks or months, the question 
naturally arose, what sanitary conclusions might be drawn 
from this phenomenon. We must first consider that the 
purity of drinking water is of by far the greatest importance 
when an outbreak of an epidemic takes place. Thus I see 
no reason to alter the opinion which I have frequently ex¬ 
pressed, that even the water supplied to London from the 
Thames, polluted as we know it is by all kinds of filthy 
matter, is at ordinary times fairly wholesome. But as soon 
as an outbreak of an epidemic, say of cholera or typhoid, 
or perhaps, according to a resent notion, of diphtheria, takes 
place, the aspect is at once changed. That same shallow 
well or river water, which had been taken with apparent 
impunity for years, becomes the vehicle, and increases 
apparently in a ratio to the state of its purity the virulence of 
the contagion. If then, I repeat, by some means or other, 
the character of the water be so changed that it does no 
longer contain fermenting matter, what is the bearing of 
that result upon the specific virus by which it has been con¬ 
taminated ? 
Assuming I had succeeded in showing the probability of 
an increase of the virulence of contagia by surrounding fer¬ 
menting matter, the answer is obvious. But even should 
that connection not be thought sufficiently established, those 
who accept the germ theory of contagia will consider it not 
unlikely that the agent which is capable of destroying one 
form of the lowest organic life may be capable of destroying 
another. Such was the line of argument leading to the ex- 
* ‘Proceedings of the Royal Society, No. 180, 1877, and No. 180, 
1878. 
