Page 138 - My FlipBook

cay, and Dr. Williams of London has shown, and we may
show our own slides on the screen, of teeth that are faulty,
worn teeth from people of adult age, teeth from people of
middle age, teeth from people of old age that have faults in
the enamel that pass through to the dentin and yet have not
decayed ; all of the usual opportunities were there, and yet
caries did not occur. And, again, I have pointed out that there
are certain things observable in the mouth by which we can
tell as we become acquainted with them, as we become ac-
quainted with faces so that we can tell this or that person
from another person by the appearance of the countenance
;
there are certain appearances in the mouth, certain
expressions that tell very certainly the coming of
immunity to decay. I have pointed out to you that

this was a general darkening of the expression of the teeth,
the teeth become more opaque and there is an inclination to
a darkening of the teeth that points out very certainlv the
coming of immunity to decay. Following up these ideas, Dr.
Michael of Paris has recently made a long series of studies
of the saliva to see whether or not he could find anvthing in
the saliva of a material nature that might have any influence
in this direction, and, following up the studies of the blood
and the studies of the secretions that have been made by
others along somewhat similar lines. Dr. Michael finds that
the cachectic conditions are reflected in the saliva ; the condi-
tions which render persons liable to this group of diseases or
that group of diseases are reflected in the material constitu-
tion of the saliva; that it is continually changing, changing
with the condition of the body of the patient. This fluid is a
secretion from the blood and the material elements of the
saliva are changed as the conditions of the blood and the
body juices are changed. In the study of the saliva he finds
the reflection of these conditions in material form that can be
studied and noted. And in this he finds, with reference to
caries of the teeth, that in the hypo-acid condition, where
ammonia is more prominent in the salivary fluids, decay of

the teeth is active, but in the hyper-acid conditions the
sulphocyanides are in undue proportion and there is im-
munity to decay of the teeth. Now you will note, in think-
ing over your chemical studies, that the conditions that Dr.
Michael has found in the material constitution of the saliva