the connective-tissue of the pulp had retained its myxomatous character, and no sign of a former inflammatory process was observable, except where the pulp had been cut in the amputation.

This result induced me to try the same procedure in fifteen other cases, although microscopical examination of pulps treated with arsenious acid and extirpated with the broach had given evidence of the destruction of the medullated nerve-fibres as far down as the apical portion of the pulp. These pulps, however, without exception, had been removed on account of pulpitis, and I was, therefore, unable to determine whether the degeneration of the nerve-fibres was the result of the application of arsenious acid, or of a preceding inflammatory process.

The results obtained from the other experiments I made with Witzel's method of amputation, were, however, not so encouraging as in the case mentioned above. I have seen eleven of the remaining fifteen cases experimented upon since last October, but the pulpstumps in every one of them had died, although the external appearance of the teeth was perfect.

The above-mentioned facts make it evident, therefore, that the minute microscopical examination of the changes effected by arsenious acid is to us of the greatest importance. They can best be studied in healthy or superficially decayed teeth of human subjects, or in the teeth of such animals as can be easily experimented upon. In all cases, therefore, a mode of procedure must be chosen, and the line of study is necessarily experimental, and should extend over a long period of time, calling for no inconsiderable amount of labor and painstaking care. Let this, therefore, be my excuse for communicating only a portion of the results obtained, which I shall take care to enlarge and detail at the earliest possible time. From my opening remarks and your own experience, you will know how important, practically, is any knowledge upon this subject. I have no hesitation, therefore, in laying before you this fragmentary communication.

The arsenious acid preparation which I have used exclusively is the well-known one composed of one part of arsenious acid and one part of sulphate of morphia, made into a paste with chemically pure carbolic acid, which was put into a drill-hole in the tooth and covered with a temporary stopping, such as cotton saturated with sandarac varnish, etc. I will not enter into details, but will only mention that, bearing in mind the results I wished to obtain, I drilled in the direction of the pulp-chamber, but did not in any case perforate it. It appeared to be quite immaterial, however, how thick

was the interposing dentine in respect to the changes caused by the poison.

I used human teeth and those of rabbits. They were extracted in from three to six days after the arsenious acid was applied. The teeth were opened immediately after extraction and immersed without delay in the proper reagent. It is very important to proceed in such manner that the pulp shall not be torn or dislodged, and yet may be acted upon by the fluids while still lodged in its natural position. When the elements of the pulp are once sufficiently fixed then only is it possible to cut (or tease) it without causing a great number of artificial changes. This is the first rule, I may say, which must be strictly adhered to by the student of so delicate an object as is the pulp. This is no easy matter, for unluckily the hardening fluids most generally in use themselves cause considerable changes; even water, and as has been found, the tissue-fluid itself, if allowed to act a sufficient time after death, gives to the medullated nervefibres an appearance which I have no doubt has frequently been described as pathological. Should I enter here upon the difficult task of describing the action of reagents, I would take up too much of your valuable time, and I am sure, furthermore, that I would tell many of you what you have known before. I will, therefore, say that after having used different other reagents, I have come to the conclusion that the very best results can be obtained by immersing the tooth in the manner described in a one per cent. solution of hyperosmic acid for from ten to twenty hours, according to the density of the tooth. As regards the pulp, this will be found to be sufficiently hardened after a sojourn of two to three hours in the same fluid; it can then be easily removed from the pulp-chamber without fear of serious harm. Both parts are then placed in distilled water and preserved in alcohol. I have, however, invariably examined the pulp, teasing it with great care, as soon as washed, after sufficient hardening in hyperosmic acid. The changes here are truly remarkable. Firstly, if the poison has acted sufficiently long, the whole of the pulp shows to the naked eye, as soon as exposed, all the signs of active inflammation.

I shall not enter into details of the appearance which such pulps present, but shall confine myself to a description of the alterations found in the medullated nerve-fibres. According to the degrees of inflammation resultant from the irritation which the arsenious acid undoubtedly does produce, a greater or less number of nerve-fibres are changed in appearance in such manner that their myelin is sepa

rated into larger and smaller masses, between which I have not been able as yet to distinguish either an axis cylinder or an intermediate substance. I may, however, mention that I have seen in nerve-fibres which have remained under the influence of the arsenious acid for six days a granular substance which can be colored by rose aniline. When the poison has acted for the last-mentioned period all vestiges of myelin have disappeared and in their stead are found smaller and larger globules, which are stained a deep black by hyperosmic acid. I will not venture to advance an opinion as to the nature of these bodies. Thus much, I dare say, however: they are certainly a product of the disintegration of the myeline sheath. I have no doubt. that this is a stage in the complete destruction of the nerve-fibres, and I may mention in this connection that, in one instance, I have found similar globules free in tissue surrounding a number of degenerated nerve-fibres in an incisor of a rabbit after three days' reaction of the arsenious acid.

You will no doubt agree with me that even this is far from complete, but you will at the same time be forcibly reminded of similar results found by many histologists after section of peripheral nerves in other parts of the body.

What will be the result of the arsenic so applied, not alone to the pulp itself, but as regards the nutrition and life of the whole tooth, is easily surmised, and can be demonstrated clearly by an examination of the dentine.

After having treated the newly extracted tooth with hyperosmic acid, and thereby guarded against artificial changes, I prepared ground specimens of the same. These were then stained with picro-carmine and suitably treated for mounting in Canada balsam. I purposely abstained from decalcifying these specimens, for, unless this process is watched with great care, the result in most cases will be, to say the least, very problematical. I have found that for the closer study of the dentinal canaliculi and their contents-the Tomes fibres-all decalcifying agents are out of place.

A superficial view of such specimens shows that hyperosmic acid has been reduced in certain places, whereas others appear colorless. Let me say at once that the former are regions of pathological changes. They start either directly from the place of contact. with the arsenious acid, and extend varying distances into the dentine, according to the time of the reaction; or, as is evident where they can be traced as far as the pulp, they radiate apparently from the latter and extend toward the periphery. Viewed under the

microscope the dentinal canaliculi are very much enlarged, more so at one place than at another, and they appear to be filled with a mass deeply stained in black. The same can be said of the transverse connections of the canaliculi. When, however, high powers (onetenth of an inch immersion of Grunow, N. Y.) are brought to bear on such places, the black mass is found to be composed of irregularly-shaped bodies, which I doubt not are remnants of the dentinal fibre. For, in following up such canaliculi, it can be distinctly seen that the greatly swollen dentine-fibres are broken up more and more as one approaches the seat of the greatest destruction. As a consequence, the basis-substance is very much narrowed in extent as the canaliculi gain in diameter. Moreover, it appears that the lime-salts are dissolved. I incline to this view because of the peculiarity of coloring, a matter into which I deem it advisable not to enter more fully just at present. I may add that, in such places, when the canaliculi are in transverse view, all these conclusions are fully borne out.

So far do I feel justified in entering upon this important subject today, although there are many points which I have thought best to lay over or only to touch upon. I am well aware, and should be prepared to hear, that the microscopical changes in the dentine are similar to those found in dental caries. It is well that in dental pathology, as well as in general pathology, due reference should always be made to the clinical aspect of the disease, and it is not less than presumption to classify together pathological units, with our present methods of investigation, enormous as has been the progress in this direction of late years. I am, therefore, far from identifying the changes here under consideration with those found in dental caries.

I am also aware that in very many cases, apparently, the effect of arsenious acid has not been so bad as might be expected, but on the other hand, you may all remember severe cases of local or even constitutional disturbances which could not be traced to any other cause than a dead tooth which had been treated with arsenious acid. Be this as it may, the question is certainly in order, whether, in view of the serious consequences, we are any longer justified in destroying pulps by the use of arsenious acid, and the answer must be that the risk is too great for the gain.

DISCUSSIONS.

Dr. PEIRCE: I have been much interested in the specimens of Dr. Bödecker and his explanation of them, but it seems to me that it is

unsafe to state that the arsenic has produced certain results when we are not sure what results would have taken place by devitalization from other causes. We are all aware that tissue does not remain quiet a moment. The instant there is devitalization changes take place, and therefore when we assert that these changes are due to the presence of arsenic we need, it seems to me, to know what would have been the appearance had devitalization occurred without the presence of arsenic.

Dr. BÖDECKER: I can only say that after three days' reaction of arsenious acid through a comparatively thick column of dentinal tissue, the inflammatory reaction which you have seen under the microscope was brought about. I do not think that any local irritation of the dentine could possibly have produced it; at least I have never seen it. I have seen hundreds of pulp-specimens which had been under the effects of irritation from caries, but in these cases I have never seen anything like this. The whole pulp-tissue is affected by the use of arsenious acid.

Dr. HORTON: I would like to know what tooth that was, whether a molar, bicuspid, superior or inferior, and the age and sex of the patient?

Dr. BÖDECKER: This particular specimen, I believe, was from the mouth of a young lady about twelve or thirteen years of age, and the tooth was a first lower molar.

Dr. WATKINS: I would like to ask Dr. Bödecker how much arsenic he puts into that pocket?

Dr. BÖDECKER: It does not make any difference how little of the arsenious acid is applied. I put in just as little as was possible, but always obtained the same reaction.

Dr. WATKINS: How long would you leave it there before removing it?

Dr. BÖDECKER: I have stated this in my paper,-from three to six days.

Dr. WATKINS: If you leave it in longer than three days there is great danger?

Dr. BÖDECKER: Of course, the longer the arsenious acid is left in contact with the tissues, the greater the danger.

Dr. ALLPORT: I would like to ask Dr. Bödecker whether he regards this change in the pulp as due to the presence of arsenic transmitted through the tubuli to this tissue, or to a transmitted pathological condition from the dentinal fibres, consequent upon irritation of their extremities from the presence of arsenic at that point.