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Not to detail all the attempts, I may come to the report to 
the Cattle Plague Commission in 1866, in which I give 
some general views and allude to the works of others. 
The following may he quoted : — 
“ It has often been asked — Will a sewer produce cholera, 
or plague, or cattle disease ? We cannot say so, or that 
every kind of disease may be produced from such accumu- 
lations of organic matter. The great epidemics that have 
passed over Europe seem always to have come from some 
extraneous source, to act as if planted by some seed , and 
not to have risen up spontaneously here. Without attempt- 
ing to examine this matter carefully, the result would seem 
to be, that whilst the decomposition of organized beings 
after death produces gases and vapours that are opposed to 
health, these gases or vapours are incapable of originating, 
although they may be capable of feeding, some of those 
diseases, such as cholera or plague, which have been 
observed at all times to come from a warmer climate. 
There must, however, be some first origin of these diseases, 
and we cannot prove that the first origin might not take 
place in our climate, although it seems probable that it 
requires a warmer sun and a richer vegetation than is to 
be found in the north. This, however, is sufficiently made 
out — that, when these diseases do come amongst us, they 
take root with most effect in those places where decomposing 
matter is found. If we were to suppose a seed of disease 
planted in a rich, fertile soil of decomposing matter, we 
should give a pretty fair description of the fostering effect 
of impurity on disease. It would in fact appear as if the 
putrid matter itself took the disease, and transferred it to 
the living. There seems to be nothing entirely opposed to 
this view of the case. The question, however, is and has 
always been — What is the nature of that substance which 
may be said to form the seed or germ of the disease ? 
Chemists have been inclined to consider it a substance in 
