appeared in a local newspaper concerning the above hospital. As I have no control over the columns of any newspaper, and certainly none over those of your contemporary, I am consequently not responsible for the "puff" referred to. I enclose a list containing the names of the gentlemen connected with the Newcastle Dental Hospital.

With regard to my qualification and of what college,
I am, &c.,

43, Blackett Street, Newcastle-on-Tyne;

April 12th, 1881.

G. F. TATE, L.D.S.I.

We insert Mr. Tate's disclaimer with great pleasure, and feel bound to add that the paper he encloses shows that the institution referred to, of which he is the Dental Surgeon, is managed by a highly respectable committee. We append the paragraph on which our remarks were founded, first because it is a typical example of "how not to do it," and secondly, that our readers may see that we had some justification for our not very friendly notice. The fact that Mr. Tate is content to undertake single-handed all the work of a hospital which is open free on three days in each week, shows that he is possessed of plenty of energy, and this is pretty sure to lead to success in any walk of life. ED. B. J. D. S.

'My readers will be glad to learn that a Dental hospital for the treatment of diseases of the teeth for the suffering poor of the North of England is about to be established in Newcastle. Under the prevailing system professional Dental attendance is not always within the reach of all classes, and too often those who are suffering from diseases of the teeth fly to the nearest chemist's shop for alleviation, where in six cases out of a dozen the inexperienced and experimenting operator does more harm than good to his patient. Medical men, too, have but a superficial and theoretical idea of this description of work, and in cases where tumours exist it is absolutely dangerous to permit of unskilled treatment, for every risk is run of thwarting and frustrating the designs and discoveries of Dental science. I feel glad, therefore, that an institution of the kind is about to be established so near at hand, and, further, that the honorary appointment of Dental surgeon to the Hospital has been conferred on Mr. G. F. Tate, L.D.S.R.C.S., Blackett Street, Newcastle (son of Mr. Wm. Tate, Sunderland, inspecting engineer for the Earl of Durham), a young gentleman of unlimited experience, gained not only in a wide practice in his native country, but on the Continent of Europe, and at the Court of Egyptian Royalty," &c.-Sunderland Daily Post.

VOL. XXIV.

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To Correspondents.

Communications intended for insertion in the ensuing number must be forwarded to the Editor, at the Office, 11, New Burlington Street, London, W. by the 8th and 23rd of the month, hey cannot be published in the ensuing issue; they must also be du.y authenticated by the name and address of the writer.

2. We cannot undertake to return communications unless the necessary postage stamps are forwarded.

3. It is earnestly requested of our correspondents that their communications be written on one side of the sheet only; and we also beg to call particular attention to the importance of a carefully-penned signature and address. 4. All communications relative to subscriptions and advertisements are to be addressed to the Publishers, Messrs. J. and A. Churchill, 11, New Burlington Street, London, W.

5. The Journal will be supplied direct from the office on PREPAYMENT of subscriptions as under :

Twelve Months (post free)

14s. Od.

Post-office Orders to be made payable at the Regent
J. and A. Churchill, 11, New Burlington Street, W.
sent on receipt of seven (penny) stamps.

ANSWERS TO CORRESPONDENTS.

Street Office, to A single number

"C. B. S." (Brighton).—We see no reason why we should congratulate you publicly. The additional capital letters which you are entitled to place after your name may carry some weight with a certain portion of the British public, but from a professional point of view, with which alone we are concerned, we feel assured that your original diploma is at least as highly appreciated as that which you have thought fit to add to it. W. SMITHARD, L.D.S.-For obvious reasons we can only publish such lists when they are received from an official source.

Messrs. WILLIS, WEBER and STOREY are thanked.

Communications have been received from Messrs. T. Ken Underwood (London), G. H. Crowther (Wakefield), Thos. Gaddes (London), H. B. Mason (Exeter), J. F. Pink (London), W. B. Macleod (Edinburgh), G. F. Tate (Newcastle-on-Tyne), G. Brunton (Leeds).

BOOKS AND PAPERS RECEIVED.

'Dentists' Register,' 1881.

'L'Odontologia.'

Correspondenz Blatt für Zahnarzte.'

Deutsche Vierteljahrsschrift für Zahnheilkunde.'
Lancet.'

'British Medical Journal.'

'Medical Times and Gazette.'

'Missouri Dental Journal.'

'Pharmaceutical Journal.'

'Specialist.' &c.

NOTICE. We desire that it may be clearly understood that our pages are open to all for free expression of their views on matters connected with our profession. We only ask for terseness of expression and MODERATION IN TONE.

When otherwise unobjectionable, difference of political or other opinion will never be regarded by the Editor as a disqualification for the admission of any communication to the. pages of the BRITISH JOURNAL OF DENTAL SCIENCE.

Delivered at the National Dental College during the Winter
Session, 1880.

By THOMAS GADDES, L.D.S. Eng.,

Lecturer also on the Elements of Histology; Assistant Dental Surgeon to the National Dental Hospital.

LECTURE VI.

Hard unvascular dentine.

We now come to consider hard, unvascular dentine, which is a highly elastic substance, of a white colour with yellow tinge, and to some extent translucent. When broken a

silky lustre is seen upon the fractured surfaces, which is mainly due to the presence of air in the tubes, and this condition is more apparent in dry than in fresh dentine. The structure of true unvascular dentine is an organic matrix richly impregnated with calcareous salts, and everywhere permeated by parallel tubes, which, for the most part, run at right angles to its external surface.

The chemical composition of the matrix will necessarily vary in different individuals, and also notably in the same individual in youth and in old age-this latter difference being due to the greater impregnation of the older matrix with calcareous salts.

The analysis of an adult molar of man, given by Bibra, which was quoted by Professor Owen in 1845, also by Mr. John Tomes in 1848, and again by Mr. Charles Tomes in his Dental Anatomy,' will be found in the table given in Lecture III.

The organic basis of the matrix is a gelatinous substance, and is closely related to that of bone, with which, however, it is not identical. It is of firmer consistence, and does not readily yield its gelatine on boiling. It has also been called dental cartilage.

By submitting a tooth to the slow action of dilute acids

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31

the earthy matter is removed, and the form and some of the structural characteristics are maintained in a soft, tough, semi-elastic mass. The normal matrix of a perfectly-formed tooth is uniform and transparent; no trace of cellular or other structure can be detected, save the dentinal tubes.

The dentinal tubes.-In the general description which I have just given of dentine, I said that the tubes ran for the most part at right angles to the surface of the dentine; but the precise direction of the tubes varies in different parts of the tooth. Each tube starts by an open circular mouth upon the surface of the pulp cavity. Thence it runs outwards in a direction generally perpendicular, or at right angles to the surface, towards which, however, it becomes smaller and breaks up into branches at a little distance beneath the surface of the dentine. So the diameter of the tubes is greater at the pulp extremity than at the periphery. In man the diameter of the dentinal tubes ranges from 0 to Too in. The course which the dentinal tubes pursue is not perfectly straight, but they describe certain curves known as the primary and the secondary dentinal curves. The primary curves are longer, describe segments of larger circles, and are fewer in number than are the secondary curves, and they have been likened unto the italic letter f-indeed the line of beauty. The number of primary curves described in a human tooth averages from two and a half to three and a half from the pulp to the periphery.

The primary curves in the root of a human tooth are sharper and a little more numerous than in the crown. Remembering that the tubes run parallel with each other, and, consequently, that each tube bends at the same distance from the surface, this coincidence in the primary curvature of the dentinal tubes gives rise to peculiar shadings, or slight differences in colour and opacity, which have been termed the lines of Schreger. These lines of Schreger, then, are not substantive, but are merely shadings or markings ranged parallel with the surface of the dentine, and are due to the coincidence of the primary curvatures of the dentinal tubes, which by their obliquity reflect light differently. The description of the lines of Schreger, given on p. 24 of the 'Dental Student's Note Book,' is an error for which I am responsible. Other markings or lines are seen in dentine. These were described by Owen as "contour lines," and his description of those markings included the lines of Schreger, and other striæ and laminæ totally different from those shadings. So, to avoid the confusion arising from calling two distinct conditions by one name, we must let the lines of Schreger be understood in the sense, and as representing

the condition I have described; and understand by the "contour lines" certain layers of dentine in which calcification is incomplete: That is to say, over the entire area of the developing pulp a layer of dentine will be formed and its calcification completed, and then another layer will form in which calcification is less complete, the impregnation with earthy salts being partial and defective, and so on alternately. These areas of imperfect calcification are made up of interglobular spaces, and they would appear to indicate the periodicity of different degrees of development. The formation of interglobular spaces I shall explain when we come to treat of development.

Mr. Salter objects to the term " contour lines," inasmuch as they only approximate remotely to the contour of the tooth. He looks upon these markings as indications of the incremental development, as showing the successive portions by which the tooth is built up, and he calls them "incremental lines." We shall by-and-bye see that interglobular spaces of which these incremental lines are but a conglomeration are abnormal conditions, and consequently such an abnormality will not justify us in considering the dentine as a laminated tissue, as Mr. Salter does.

The secondary dentinal curves are very much smaller and more numerous than the primary curves. As many as 200 secondary curves have been estimated in in. The cause of these slight undulations is probably due to the line of development taking place in a spiral direction, and the effect of an elongated spiral viewed on its side will, of course, be only slight undulations such as the secondary curvatures of the dentinal tubes present. As we saw, the primary curves were sharper in the root of a tooth, so also are the gyrations termed secondary curves more strongly marked in the root.

As the tubes pass outwards from the pulp-cavity they often divide into two equally large branches; they also give off fine branches, which anastomose with similar branches from neighbouring tubes. For the present I shall use the term branches, but, when the histological formation of the tubes is considered, we shall see that such are not branches from the tubes, but rather that the tube or trunk is to be looked upon as a confluence of the earlier formed tubes or so-called branches.

In the crown of a human tooth these fine branches are comparatively few, until the tube has reached nearly to the enamel; but in the fang they are so numerous as to afford a ready means of distinguishing whether the section is from the root or crown of a tooth.

Owing to their breaking up into minute branches, some of