Page 68 - My FlipBook

there tetanus occurs frequently. It is an organism very much ;;
to be dreaded.
Strict saprophytes will not g-row in the bodies of animals
under any known conditions ; they are confined to dead or-
ganic matter entirely ; they will take hold of dead bodies very
quickly and cause their decomposition rapidly, but will not
grow at all in the living body.
The parasitic micro-organisms are again divided into
strict parasites and facultative saprophytes. This is a more in-
teresting field, perhaps, to us, for many of the micro-organ-
isms that we find habitually growing as parasites may be
grown artificially, and, of course, in that case are growing as
saprophytes—they are facultative saprophytes. The great
ibulk of pathogenic micro-organisms belong to this class
otherwise, we- could not grow them artificially we could not
;
study their life history.
There are, however, many strict parasites and quite a
number grow in the human mouth, and in these we are es-
pecially interested.
A strict parasite is one that will not grow, or has not
l)een known to grow anywhere else than in the bodies of
animals, or in the body juices or secretions in loco. Now
understand what I mean by this term in loco—a Latin term
meaning in place, in the saliva, for instance, while it is still
in the mouth ; in the urine in the bladder ; in the secretions in
their normal positions. There are five or six micro-organ-
isms that grow habitually in the human saliva that will not
grow in the human saliva after it is removed from the mouth
we cannot even use the saliva as a culture medium out of the
mouth. That is what we mean when we speak of an organ-
ism as a strict parasite; it is so particular as to its habitat that
'we cannot grow it anywhere out of its normal abiding place.
Micro-organisms are again divided into indifferent
Aerobic, Aerobic and Anaerobic. This has reference to their
necessity for oxygen or air.
The indifferent aerobic micro-organisms are those that will
grow with or without oxygen, and this is very much the
larger class. Almost all of the pathogenic micro-organisms
will grow with or without oxygen. There are some, however,
that will not grow until air is admitted to them. These zve call
.aerobic micro-organisms ; they require air. The other class, the

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