much during the period when they were shedding and giving place to the corresponding number of permanent teeth, but must have continued about the same dimensions throughout. But as room must be formed in the jaws of the adult, behind the place occupied in the child by the last molar teeth, that is, in a part where no teeth existed before, for the lodgment of the large permanent molar teeth; and as that can only be obtained by a proportionate addition being made to the jaw-bones at that part, it follows, that the growth must proceed with great activity at the posterior division of the jaws during the rising of the molar teeth. The degree of that activity of growth, compared with the rate in the anterior division, may be estimated by observing that the size of the part of the jaws which contains the molar teeth, is about equal to that which contains all the others situated anteriorly.

It is obvious, therefore, that if, while the evolution of the teeth is still going on, the growth be interrupted for a time, the effect will be greatest upon those portions of the jaw-bones which grow at the quickest rate; that is, upon the posterior portions containing the permanent molar teeth, than upon the anterior portions. That such is the case, at least as regards the superior maxillary bones, we have already had evidence of an indirect kind to prove. It was shown, when treating of the effect produced on the size of the orbits by the frontal and maxillary sinuses becoming developed to a greater or less degree in

proportion to the activity of the growth, that these sinuses were remarkably diminutive in persons retarded in their growth by rickets. Now as the maxillary sinuses are in anatomical relation at their inferior parts with the divisions of the jaw-bones superadded to give lodgment to the permanent molar teeth (for the alveolar processes of these teeth together form the floors of each of the sinuses), it follows that when the sinuses are generally small, the parts in which the molar teeth are contained must likewise be small. Hence, the obvious effect will be, a want of due proportion between the size of the molar teeth and that of the portions of the jaws intended to lodge them-the teeth will be too large for the jaws, in these parts.

The above views seem to me not undeserving the attention of those members of the profession, who, from the particular department of practice which they follow, have more ample opportunities than others of observing the derangements of health commonly supposed to depend on a disturbed state of the process of dentition. It is also to be conceived that they will be interesting, in a peculiar manner, to the dentist.

Since they occurred to me, I have not had sufficiently extensive means of judging how far they may be applied with advantage to the elucidation of disease, so as to express any confident opinion on that subject. But I will offer the following remark as a suggestion to those who may intend prosecuting

the inquiry. In observing the diseases of children which take place at the period of teething, we are perhaps too much in the habit of referring the derangement of health to the condition of the teeth; as if the difficulty and pain in protruding the teeth above the gums were the first and original cause of the disorder. It may perhaps be found, by pursuing our observations with more care, that the constitutional irritation proceeding from this cause is a secondary, rather than a primary object of our attention. It is not improbable, in short, that the disturbance in the process of dentition has itself resulted from previous constitutional derangement. It may happen that, owing to a bad state of the health analogous to rickets, and independent of the state of the teeth, an interruption may have been produced in the growth of the maxillary bones; and from that has arisen a want of correspondence between the size of the teeth and of the bones, sufficient to account for the derangement of the teething.

Before quitting this subject, I beg to refer to the valuable researches of my colleague Dr. Ashburner, into the question of the influence of protracted and difficult dentition, in giving rise to various obscure forms of disease in persons more advanced in life than children. It appears to me that the views brought forward in the present paper, may throw considerable light on the causes of the want of relation between the size of the jaws and of the teeth,

to which that gentleman attaches so much importance, in explaining the derangements to which he refers.*

In conclusion, I may here give a short description of a remarkable condition of the teeth and jaws, which I have had the opportunity of observing since beginning this paper, in a patient greatly distorted from rickets, who is at present in the Middlesex Hospital. I have observed in numerous persons deformed from that disease, great crowding, accompanied with much displacement and irregularity, of the teeth in both jaws, apparently produced from want of proportion between the size of the bones and that of the teeth; but in none have the effects been so distressing as in the case to which I refer. The patient is a girl, seventeen years of age, who was admitted into the hospital under the care of my colleague Mr. Arnott, for fracture of the left thigh bone. Her whole body is distorted in the manner usually seen in those who have had rickets in early childhood, but to an aggravated degree such as we seldom witness. On looking to the curved and twisted state of the legs, it is only surprising that she should have been able to walk before she met with the fracture. In regard to the appearance of the head, it is particularly remarked that it has the proportions of the child about six or eight years of age, instead of those of a person of her time of life;

* On Dentition, and some coincident Disorders. By John Ashburner, M.D. 1834.

and so much does this peculiarity in the proportions of her head deceive those who are asked to guess her age, that she is invariably supposed, at first, to be only about eight years old. Both jaws are remarkably small; and the teeth present several irregularities. The first thing which attracts our notice, is the disproportionately large size of the crowns of the front teeth when compared with the smallness of the jaw-bones. The next, is the great number of teeth which are wanting, without there being sufficient room to receive additional ones. Although the patient has arrived at that period of life when she ought properly to have the full complement of permanent teeth, she has only fourteen teeth altogether in both jaws; and the vacant spaces which mark where the teeth that have dropped out were formerly placed, are all so narrow that it would be impossible for them to contain a sixth part of the teeth that are lost. Another circumstance marks in a striking manner, by the distressing effects to which it gives rise, the want of correspondence which must have existed, during the growth, between the development of the teeth and of the jaws: although the crowns of most of the teeth, as already mentioned, are large enough to be adapted for jaws of full size, the fangs are extremely small, and the sockets correspondingly shallow and imperfect; the consequence of which is that these teeth are all quite loose; so that they can be easily shaken to and fro with the fingers, and it is with great pain and difficulty that she chews her food.