the tubes become lost as they approach the surface of the dentine, and apparently end in fine-pointed extremities; others terminate by anastomosing with terminal branches of neighbouring tubes, forming loops, both near the surface of the dentine and also deeper in its substance. Some tubes pass into small interglobular spaces, which are found in great abundance upon the surface of the dentine in the roots of teeth, and in which situation, from the consequent granular character of the tissue, such is called the "granular layer." This granular layer, being the part of the dentine first formed, is necessarily contiguous with the superjacent tissue of the root-the cementum. Some of the canaliculi from the lacunæ of the cementum communicate with the spaces in the granular layer, as do some of the dentinal tubes, and thus a connection between the dentine and the cementum is not infrequently established. Indeed, there may occasionally be seen direct communication between a dentinal tube and a canaliculus.

From the existence of the interglobular or granular layer upon the surface of the denture in the roots of all human teeth, it is looked upon as a constant condition; but when it is present in the crown it must, from its rarity and histology, be looked upon as abnormal. So also must the passage of the dentinal tubes into the enamel be regarded as exceptional and almost pathological in its nature. It was first demonstrated by Mr. John Tomes that the passage of the dentinal tubes into and through a great part of the thickness of the enamel was characteristic of the order Marsupialia; the wombat excepted. The passage of the dentinal tubes into the enamel has also been found in the jerboa (a rodent), and in Soricidæ (shrews) among Insecti

vora.

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As to the contents of the dentinal tubes there has long been diversity of opinion. Mr. J. Tomes, who first demonstrated the contents of the dentinal tubes, called such contents "dentinal fibrils." Mr. Salter objects to such a term, and says their contents are a "dense plasma." But this difference almost entirely resolves itself into a quibble as to the term, for both agree that the contents are prolongations from the odontoblast in the pulp. The nature of the dentinal tubes and of their contents I think it well to defer till we treat of development, when their description will take its proper place as in the histological formation of the tooth.

Regarding the tubes I shall only add in conclusion that, according to Dr. Beale, they are not tubes in the same sense as the canaliculi in bone are tubes; they do not convey nutrient fluid, they are simply tissue in a transitional condi-

tion between "formed material" and perfectly "calcified formed material;" and their contents, likewise, must be looked upon as a yet younger transitional tissue-the filament or process from the odontoblast, which has not yet become calcified. So by removing this youngest material, or contents of the tubes, there is left behind a harder surrounding material, the so-called sheath of Newmann or wall of the tube, which is embedded in the calcified matrix.

[The writer much regrets the want of time to prepare the more necessary illustrations to these lectures.]

Dental Surgery and Medicine.

ON THE MODE OF ORIGIN OF SOME SECONDARY LESIONS IN RELATION TO DISEASES OF THE TEETH.

A paper read before the Students' Society of the National Dental Hospital and College, March 11th, 1881.

By EDWARD W. Cox MOORE, L.D.S.R.C.S.I.

MR. PRESIDENT AND GENTLEMEN,-In most books on Dental Surgery a considerable amount of space is usually devoted to a description of the nervous affections which may result from the condition of the teeth, these diseases occurring in some cases where a healthy tooth is undergoing normal development, and in others where we have to deal with a tooth which has undergone decay, or one in which some new growth presses upon the nerves in connection with the tooth. This subject is one which it is difficult to handle from a purely Dental point of view, owing to the various structures which have to be brought under consideration and the variety of diseases that may affect those different struc

tures.

The object of this paper is not to give a résumé of the multiform diseases resulting from irritation in and about the teeth, but rather to investigate the question as to the mechanism by which some of the more complex cases of reflex irritation, with the resulting lesions, can be explained and shown to be parallel to the mode of production of other diseases in the body. It will perhaps simplify matters to com

mence by giving a few examples of the special form of secondary disease which it is the object of this paper to elucidate. The first example we take is one related by Mr. Hilton of the late celebrated Dr. Addison.

"The latter was suffering from an offensive discharge from the auditory canal of one of his ears, which annoyed him very much, and below the external ear was a small gland enlarged in the upper part of the neck. He had tried various remedies for this discharge, and had gone, I believe, to some surgeons who made a specialty of diseases of the ear, but as far as I could judge no good resulted from any of their applications. Upon examining the ear from which the offensive discharge proceeded, I found a slight ulceration upon the floor of the auditory canal. On arguing the question out between us, we came to the conclusion that the ulceration probably depended upon a diseased molar tooth in the lower jaw on the same side. We had that tooth extracted, and in a very short space of time the ulcer healed, the discharge and morbid secretion disappeared from the auditory canal, and so soon as that ulceration was cured, the enlarged gland subsided."

In this case the symptoms, though troublesome, were not dangerous but we pass on next to a class where more important structures are affected, so ably described by Dr. Woakes in his work on 'Deafness, Giddiness, and Noises in the Head,' viz.:

"A child is cutting its teeth, and while the gums are yet swollen it suffers acutely from earache; any one accustomed to watch carefully the symptoms of these little patients will scarcely fail to discern in the troubled face, the thrill of agony, accompanied with cries or shrieks, when its position is moved, and above all the constant raising of the hand to the side of the head; no one who has watched these symptoms will fail to connect them with the most agonizing sufferings of early life-' earache.'

"On examining under these circumstances with the speculum, in a good light, the drum of the car, it will be found to have exchanged its pearly-like lustre for one of redness; this gradually extends to the lining membrane of the cavity of the tympanum, and unless this condition be actively treated by lancing the gums and local removal of blood, the further stage is soon reached at which formation of pus commences, and the child becomes permanently deaf from bursting of the membrane, or the still more serious complication occurs of extension of inflammation to the membranes of the brain, an occurrence for which every facility is arranged by the intimate communications which, in the infant especially, exist for

such an issue, convulsions, coma, and death rapidly succeed."

Now, the point I wish to emphasise is this: the pain is not what we vaguely term neuralgia; it is a definite trophic change, an inflammation taking place in the deeper seated tissues of the ear; the gums are lanced and thereby reflex irritation is lessened.

But a child has by no means escaped ear trouble arising from the teeth if it has safely passed over the period of their evolution. External otitis has been distinctly traced in children to the presence of a carious tooth, and even in later life a decaying tooth will indicate its presence by prolonged earache and will even establish an otorrhoea. The first example I gave you was of this kind.

As another example of trophic or nutrition lesions of a more trivial kind I may mention the following, recorded by Mr. Hilton:

"A person was brought to me by a surgeon suffering very great pain on the left side of his face. He was much exposed to the weather and suffered a great deal in consequence. He had taken a good many things to cure the neuralgia' as it was termed. I observed that he wore a wig, and I asked the reason. He said, curiously enough the hair on my left temple has all turned grey. I did not like to have black hair on one side and grey on the other, so I had my head shaved and wear a wig. Upon examining his mouth, I found he had a decayed molar tooth (rather painful) on the left side of the lower jaw, supplied by the third division of the fifth nerve. When this second lower molar was extracted the neuralgic pain very nearly ceased. I have not seen the patient since, so cannot say whether or not the hair has recovered its colour. All I can say is, it was stated to me that during the time he was suffering extreme pain on the left side, the hair over the temporal region became nearly white, the difference in colour suggesting to me some structural deterioration, and to the patient the propriety of having his head shaved and wearing a wig."

Another case is related where the constant presence of fur on one half of the tongue caused a patient to seek advice. The patient was found to have a decayed molar tooth on the same side as furred tongue. The tooth was removed, and a fortnight afterwards all the fur had subsided.

Quite a different explanation has been put forward of this unilaterally furred condition of the tongue, viz. that the half of the jaw in which the diseased tooth is situated is but little used in mastication, and hence no removal of epithelium of the tongue takes place by the friction of the food on

that side. This objection is completely overruled by the following:-It is shown that the tongue was furred only over the distribution of the lingual gustatory to the anterior part of the tongue, whereas it is clear that if the furring had resulted merely from a want of use of that part of the jaw, the fur would not have been limited to the anterior, but likewise have affected the posterior part of the tongue; this part, which receives its nerve supply from the glosso-pharyngeal nerve, may sometimes be seen to be furred in cases of inflamed tonsils, which also receive branches from the glosso-pharyngeal.

Mr. Hyde Salter relates the case of a healthy young woman, from Bournemouth, who consulted him on account of an ulcer, about the size of a shilling, on the side of the neck; this had commenced some twelve months before as a painful red spot and had been treated by applications of every kind without the slightest improvement in the condition of the ulcer. Mr. Salter examined the mouth, and found the wisdom (lower) on the same side of the jaw as the ulcer to be in an advanced stage of caries; this tooth was promptly extracted and within a fortnight after the ulcer was completely cured and remained a firm cicatrix ever after.

In all the examples I have given you a definite nutritive change has been found to exist in the irritated area, whether resulting in such slight changes as the turning grey of hair, a condition found normally later in life, in the production of an excessive amount of ill-formed epithelium, or a condition of hyperæmia, inflammation, and suppuration, as exemplified in the ear disease, up to the local destruction or death of tissue resulting in an ulcer.

The question now before us is to find the solution of the various symptoms detailed. Taking the case in which inflammation of the external ear resulted from the cutting of a tooth, we have the phenomena of pain, inflammation, and suppuration in an organ widely separated from the recognised exciting cause, and with no obvious intercommunication between the two except through the medium of nerve fibres; the simple continuity of sensori-motor nerves is insufficient to produce the conditions under review. The explanation will be found in the relation of the vaso-motor nerves and the functions which it is their office to fulfil. These vaso-motor nerves have the power of altering the size of the arteries to which they are distributed, and by this means can increase the supply of blood entering the part to which the irritation is applied, or when they act so as to contract the vessels greatly diminish the amount of blood circulating.