smooth surface. If you want to introduce it with ease you must avoid angles as far as possible. Some one has said that a filling for the best service should be perfectly solid. The speaker was sure that the gentleman who made the remark was mistaken. There are fillings where absolute solidity would be a disadvantage. First, from the conduction of thermal changes, and then, from the expansion of the fillings through ordinary changes of temperature, in a little while you will find the frail edges of the enamel breaking down. He did not know if he understood Dr. Allport correctly, but there is no question that we do save teeth now with cohesive gold that the fathers condemned to the forceps. Dr. Morgan finds matrices frequently of great value in filling cavities, but stress was laid by one of the speakers on the fact that they make simple cavities out of compound ones. In the speaker's experience compound cavities were sometimes easier to fill than simple ones. Approximal cavities in the second and third upper molars, where there is considerable convexity on the surfaces of the teeth, are more readily filled without the matrix than with it, because you can see what you are doing.

Dr. Allport wished to say a word in reply to Dr. McKellops as to his method of annealing gold. Dr. McKellops asserts that he (Dr. Allport) anneals his gold and uses the mallet, and therefore he must use cohesive gold. The speaker would say that he does anneal his gold,—just a little portion of it; and he does use the mallet, because he can do so to advantage in his method of filling with soft gold; and so could others if they would try the same plan. To describe that method, suppose we make a retaining-pit (something which he seldom does). He claimed that no man could fill that retaining-pit as perfectly with cohesive gold as with non-cohesive. His way is to take the pellet and anneal a little of one end; then put the noncohesive portion of the pellet into the retaining-pit, filling it perfectly with the non-cohesive gold, and leaving the little point which has been annealed and thus made cohesive sticking out. He then puts more non-cohesive foil to this, the annealed ends of the pellets becoming in turn retaining-points.

Dr.-Kulp had had some personal experience with bridge-work. Some years ago he lost a bicuspid and cuspid from the left side of the upper jaw,* and tried some twenty artificial teeth on plates, but they were all failures. Later he lost the first upper molar on the same side of the mouth, after which mastication became difficult. His remaining molars began to abrade, and the front teeth began to push forward, one or two of them getting sore. He then tried bridge-work, which he had now worn for two years, and it had given him exceeding satisfaction, banishing the annoyance of trying to speak with a piece of plate-work in the mouth. He had since put in quite a number of bridges for his patients, and gratified them to a much greater degree than with any other method of inserting artificial teeth in all his years of practice.

Dr. J. J. E. Patrick, Belleville, 111. It is the first duty of every man to know what the materials are with which he works. We have heard here the words cohesive and non-cohesive, and adhesive and non-adhesive, used in a way to indicate that there is some confusion of terms in the minds of some of the speakers. All gold is cohesive if pure. There is a great variety of names attached to forms of gold intended for dentists' use, but they do not always indicate clearly the characteristic properties of the preparations. It ought to be the dentist's first duty to know the chemical properties of the material he is using. "Adhesive" is not properly applicable to the union of molecules of the same solid when brought into contact, for adhesion is a force which unites the particles of ^different substances. Gold possesses, in an eminent degree, the molecular force which unites the particles of the same kind of matter, and it is, therefore, very cohesive, and consequently not adhesive. Its working properties may be modified, rolling or beating driving the particles together and presenting the quality called hardness or compactness. Again, the application of heat overcomes the cohesion of its particles, and we have the property of softness. In the degrees of softness it might be called cohesive, because in this condition its particles would more readily cohere under percussion or pressure; but in degrees of hardness it might, in a relative sense, be called non-cohesive, because its particles would present more resistance to percussion than when in a soft condition. With regard to filling teeth, Dr. Patrick declared he had no system. Much time has been spent here and elsewhere in discussing the Herbst method, which is valuable as the badly-built school-house is to the architect; it shows him how to build a better. The Herbst method is a system of burnishing, and he doubted if burnishing would give as good cohesion as a blow. In his opinion? the roughened instruments were improvements over the smooth burnishers, because they give what is really the impact of a blow.

Dr. W. C. Dyer, Chicago. There seems to be a misunderstanding of the terms adhesive and cohesive gold; if pure, gold is cohesive. Adhesion signifies the union of two separate bodies; cohesion the union of like molecules of the same substance. We speak of cohesive and soft golds. Soft gold is not as soft in fact as the cohesive is after being passed through the flame of a lamp, but it seems to be softer.

Dr. W. B. Ames, Chicago, is very much in favor of eclecticism in practice, but a mixture of methods that he could hardly believe in is starting a filling with the Herbst burnishers and finishing it with the electric mallet. He could not see the consistency of placing a soft mass in the bottom of a cavity and using the mallet blow to complete the filling. By using soft cylinders, put in with hand or mallet force, one can get a proper foundation to stand the heavy blow of the mallet in finishing. In the inaccessible parts of cavities he thought we should lay the mallet aside and use hand-pressure, whether we fill with non-cohesive or cohesive gold.

Br. J. Taft, Cincinnati. The Herbst method does not stand as the only method in which the burnishing of gold into cavities has been practiced. At the International Congress in 1881 some specimens of fillings by Dr. A. A. Blount, of Geneva, Switzerland, were shown, which embraced practically the same method. In these specimens the cavities were lined with soft gold, burnished in with smooth-end instruments, the center of each cavity bei ng filled with soft gold. Dr. Blount, it was said, had used these instruments in thi& way for several years. That better adaptation to the walls was secured than by any other method then in vogue was evident tothose who saw the specimens. The cavity was prepared perfectlyr and then with the smooth instruments the gold was burnished against the wall, all around it first, thus forming a lining, instead of completing the filling as the work went on. Dr. Taft did not regard Dr. DabolPs advice to all young men to study the matrix and use it in approximal fillings as sound teaching. Dr. D. stated that its use would reduce all cavities to simple ones. If you proceed on that assumption, disaster will almost surely follow. There must be perfect adaptation of the matrix, and in some cases it is almost impossible to get it, and it requires more skill than is ordinarily employed or possessed by many dentists. He would not advise the use of the matrix where you can fill without it. Dr. Patrick said that no man ought to use any material until he knows all about it. If that rule were followed, many of us would have to go to schooL In reply to a question, Dr. Taft stated that the terms "soft" and "non-cohesive" were commonly used interchangeably. In some cases gold which is soft is non-cohesive; in others soft gold is cohesive. Some golds are very soft, and will yet weld. All we know about it is that there is a great difference in the behavior of gold under different treatment. He attributed the variations which have been spoken of to the manipulation which the gold has undergone in manufacture.

Dr. T. W. Brophy, Chicago. Cohesive gold subjected to the fume& of aqua ammonia becomes non-cohesive. It is immaterial, he said, whether he buys cohesive or non-cohesive foil. If he wants cohesive gold he anneals it; if he wants non-cohesive, he places it in a drawer in which he keeps a bottle of ammonia water. With regard to bridge-work, while it is desirable to place something in the mouththat will be strong and durable, without the necessity of a plate, he regretted to say that he had not seen anything in this direction that was satisfactory. For one or two teeth it may be all right, but where four or five, or even three, are included, it will soon result in failure. He would like to know how to secure absolute adaptation of the bands to teeth which lean toward each other. There will be a space at the bottom in which secretions will accumulate and eventually cause the destruction of the teeth to which they are attached.

Dr. W. P. Horton, Cleveland, thought the discussion had taken so wide a range that he was tempted to ask, What is it? A good deal has been said about the different kinds of gold which would have been more intelligible if we had a definite nomenclature, so that when we said a thing all would know exactly what was meant. The introduction of cohesive gold opened up a wide field, and hundreds of teeth are saved to-day where one was preserved in the old days. The Herbst method may be regarded as another important improvement. Dr. Blount did give the rotary motion in his method, but he used hand instruments instead of the engine, and did not put in the whole filling in that way,—only a part of it. We should all of us be acquainted with every method that is of value, so as to be enabled to use any part of any method wherever its use will be of advantage.

Dr. Thomas believed that Dr. McKellops, who made the remark that approximal cavities could not be so well filled without the matrix as with it, had made a great many good fillings of this class before he knew there was such a thing as a matrix. With reference to Dr. Allport's method of filling retaining-points, he should reverse the order, placing the cohesive end of the pellet in the retainingpoint. He could not see why we could depend upon the unannealed point in the pit and not in the cavity.

Section TV was passed.

Second Day.—Evening Session.

The association met at 8 o'clock. President Crouse in the chair.

The special order for the session was the report of Section Y, Anatomy, Histology, and Microscopy, which was read by Dr. Frank Abbott, of ISTew York, as follows:

Mr. President: To my knowledge there has been very little accomplished the past year in Histology or Microscopy bearing directly upon the teeth.

Of course, more or less has been done by the advocates of the septic theory of all kinds of pathological condition to which human beings are subject to prove their position correct, and by those opposed to such theory to prove them incorrect. These latter « unbelievers" have made, it appears, several rather startling points, to say the least, which favor their position, viz.: M. Ducleaux has recently sent a communication to the Academie des Sciences on "The Germination of Plants in Soil Freed from Micro-Organisms." He chose for his experiments the Dutch pea and the haricot bean, the first of which has its cotyledon in the earth, the second on the surface. The soil having been sterilized before the seed was sown, germination did not take place. This soil was also covered with milk, but this was not altered. Thus it seems that it is essential to germination that there be micro-organisms in the earth. M. Pasteur also states that he "has found by experiment on animals, that food which is free from micro-organisms cannot be digested, as they are necessary to the process of digestion."—Journal of the American Medical Association.

Comment upon the above quotation seems unnecessary. It puts a large organism into the "thinking-cap" of every thoughtful dentist.

One step toward the more perfect illustration of the finer structure of tissues has been made (so I am informed upon the best of authority), which will prove of great service to all microscopists, viz.: Strieker, of Yienna, has invented a "micro-stereopticon" (this name is mine), by which an ordinary slide may be used, and the "field" magnified to the enormous extent of 12,000 diameters, and projected upon a screen, so that a thousand people may study the tissue at the same time. The reticulum in the amoeba and in the colorless blood-corpuscle is made so plain that no one can question it. Our theories in reference to the physiology and pathology of teeth are soon to be either established beyond a doubt or are to be disproved. What a relief this will be to the strained minds of some who are particularly interested in these questions! I expect within a few weeks to have the pleasure of seeing one of these instruments and witnessing its wonderful developments.

All I have to offer for Section Y is a voluntary paper by Prof. L. O. Ingersoll, entitled "The Alveolo-Dental Membrane: Unity or Duality—Which?" and the result of some of my own work during the past year, which I present under the heading of "Studies of the Pathology of Enamel of Human Teeth."

Dr. Abbott said that, before reading his paper, he wished to acknowledge his indebtedness to Prof. Heitzmann for the very excellent drawings which he should show, and for other assistance in the preparation of the paper.

The specimens from which two of the drawings were made, he said, were under the microscopes on the table, and he would be glad if those present would examine them.