Page 70 - My FlipBook

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morning, micro-organisms are divided into pathogenic and
non-pathogenic.
Now, we have a whole lot of micro-organisms growing
in the human mouth that are of no consequence to us what-
ever, perhaps, beneficent, for aught we know ; they are non-
pathogenic. There are other classes of micro-organisms
growing in the saliva that are pathogenic ; they do certain
damage. There are others that are liable to be caught in the
saliva at any time and may be growing in the saliva of any
one of us here, that, if a wound is produced and they enter it,
will cause pus formation ; or there may be those that will
cause other diseases—cause edema, cause various inflam-
matory conditions—so that we are never safe from the patho-
genic varieties.
The non-pathogenic, although they may be parasitic, are
of no consequence. The saprophytes, of course, are non-
pathogenic generally, and yet not strictly non-pathogenic
either ; they cannot produce disease by growing in the body,
but they may produce poisons by growing in food before
we eat it that will make us sick after eating. The cases of
poisoning by ice cream, pastries and all of this are cases in
which saprophytic micro-organisms have been growing in.
the food before it is eaten and have produced poisons by the
chemical change they have induced in the material. And in
that sense a strict saprophyte may be a pathogenic micro-
organism, but only in that sense.
Some micro-organisms are pathogenic in man ; some in
cattle some in sheep ; some in rabbits ; some in mice some
;
;
in hogs, and so on ; they are, many of them, particular about
the animal in which they grow. The bacillus of diphtheria
grows in man, produces its disease in man, and also in cats,
but, so far as we know, not in other animals. The spirillum
of relapsing fever in India produces the fever in man and
monkeys, but not in other animals. And there is a certain
micro-organism that produces necrosis or gangrene in the
house mouse which has no efifect whatever and will not grow
in the field mouse, that, so far as we can see, is just like the
house mouse.
In my next lecture I will talk about the forms of micro-
organisms and show you some pictures on the screen.

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