Page 995 - My FlipBook

ETIOLOGY. 1005

change of circumstances very different from that seen when the action
takes place in the ordinary still condition, and leads us to suspect that
there may be circumstances modifying its erosive power which are not
yet known or recognized. When we come to analyze the results of
these experiments, this is all that can be said of it, so far as the expla-
nation of erosion is concerned ; for if an acid were present in the mouth
in the strength of solution that is required to produce this peculiar effect
out of the mouth, tlie teeth would be quickly destroyed. Were this not
the case, it is difficult to conceive of a current being maintained in the
mouth sufficient to effect the erosions met with in practice. Indeed,
some of the forms of erosion are such that a current could not possibly
be the cause—such forms, for instance, as are given in Fig. 534, where
there is a perpendicular incut in a half circle, or in Fig. 535, where the
teeth were eroded in the form of cups, or in many other cases that might
be given.
The possibility that erosion might be effected by something like the
absorptive processes occurred to me some years ago. Certainly a num-
ber of cases that have come under my observation have shown a peculiar
congested condition of the lip that came against the portion of the labial
surface being eroded, and it seemed probable that an acid secretion
abnormal in character was being produced at this immediate point,
Avhich, together with the motions occasioned by the lip, might effect
the solution of the substance of the tooth. In a few instances I have
seen clearly the impression of the eroded surface in the lip, showing
that it fitted into it very exactly. At the same time, litmus-paper
applied to the lip showed that the secretions at that point were decidedly
acid. This seems very near a demonstration of the cause, but I have met
with cases in which no such agency could be proven—cases in which
there is no tissue in habitual contact with the surface.
Dr. E. D. Swain of Chicago, who has taken much interest in this
subject, has made a close study of the theory of electrolysis, especially
of the ideas advanced by Mr. Bridgeman, whose experiments he has
repeated and varied, using a large number of acids, different strengths
of solution, etc., becoming finally convinced, however, that the explana-
tion is not to be found in this direction.^
While pursuing these experiments Dr. S. has made some important
discoveries in the diffusibility of acids, a table of which I have the priv-
ilege of giving. This table represents the percentage of each of the acids
named (dissolved in distilled water) that can clearly be detected as giv-
ing an acid reaction with litmus-paper :
Oxalic acid 1-260 of 1
Citric acid 1-160 of 1
Phosphoric acid 1-130 of 1
Acetic acid 1-65 of 1
Butyric acid 1-30 of 1
Tannic acid 1-30 of 1
Tartaric acid 1-260 of 1
Sulphuric acid . 1-130 of 1
Nitric acid 1-130 of 1
Hydrochloric acid 1-140 of 1
1 T am indebted to Dr. Swain for the privilege of the perusal of several unpublished
manuscripts on this subject.