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ill effect ; indeed Pasteur has suggested that they may render material 
aid in the vital process of digestion. Some of them act the part of 
scavengers, causing the putrefaction or decay of dead organic matter ; 
others, however, are accepted as the undoubted causes of such 
diseases as anthrax or splenic fever in cattle, cholera in fowls, anda 
form of typhoid in pigs : less generally, but yet by some of the highest 
authorities, consumption, cholera, and typhoid fever in man are con- 
sidered to have been proved at least within a measurable distance of 
certainty to be due in each case to the presence and multiplication in 
various parts of the human body of a specific bacillus ; some of these 
specific germs, or perhaps their spores, finding a resting place in 
a suitable subject, and reproducing as an accompaniment of its own 
enormous multiplication each its special disease, and apparently no. 
other. 
The bacillus tuberculosis is pretty firmly established ; the battle still 
rages over the ‘‘comma bacillus” of Dr. Koch, attributed by some to 
segments of the spirillum, while comparatively recently Dr. Gaftky 
has found in various organs of the human body after death from typhoid 
a special form of bacillus which was absent in only one case out of 28 
examined. 
It is also claimed that diphtheria, ague, leprosy, relapsing fever, 
pneumonia, small- pox, scarlet fever, etc., in fact all diseases hitherto 
classed as zymotic, as well as several others, are caused by the presence 
in the body of specific forms of these schizomycetes, derived either from 
air or from water, the latter being undoubtedly the chief agent in 
disseminating typhoid fever. 
The presence in water of minute organisms, in most cases, as I 
before said, harmless, but occasionally deadly, may be shown by growing 
them in various culture or cultivation fluids in which appropriate 
chemical substances are dissolved, they multiply enormously in a few 
days, rendering the clear fluid milky, and some of them can then readily 
be examined microscopically. The serum of blood, the aqueous humour 
from the eye of an ox, slices of half boiled potato and beetroot, and 
other substances, have also been used, but the best method by which their 
presence may be rendered apparent to the naked eyeis by mixing the 
water with melted gelatine jelly in a tube, adding a very small quantity 
of phosphate of soda, allowing the jelly to set, and stand protected 
from air germs by cotton wool for some days. Each point of life multi- 
plies and forms round it, either a sphere of liquid, or a gas bubble, and 
in this way different waters may be compared, at least so far as quantity 
or intensity of life is concerned, and so far as our present limited know- 
ledge goes we may assume ‘“‘the fewer the better” a general rule. 
Strong sewer water does not show globules, but the whole mass be- 
comes turbid, and liquifies from above downwards. 
The mode of action of the disease germs has been variously supposed. 
to be either a struggle for existence with the vital cells of the animal 
body, death following if the function of the parts invaded be destroyed ; 
the formation of poisonous matter in the fermentation produced by them ; 
or mechanical obstruction of the capillaries by millions ot them blocking 
the circulation. 
Definition of Good Water. 
Water for human consumption ought to fulfil all, or at least as many 
as possible, of the following conditions :—It should be almost, if not 
entirely, free from—(a) Floating matter, whether finely divided earth or 
organic matter, either animal or vegetable living or dead and decaying. 
(0) Dissolved animal or vegetable matter, or more than a moderate 
quantity of dissolved mineral matter. (c) More or less injurious or 
poisonous metals in appreciable quantity, such as lead, copper, zinc, 
arsenic, or iron, It should have no corroding or dissolving effect on 
