22

MR. MUMMERY'S DEDUCTIONS.

eruptive period; but I find a large array of facts, confirmed by my own observations, which point in my mind to this only conclusion; and, although other observers of similar facts have attempted in many instances an explanation of what they saw, they have failed to refer them to any satisfactory primary cause.

In Mr. Mummery's paper, before referred to, in speaking of diseases of the teeth, he says: "It is to be feared that a large amount of dental disease is originated by overtaxing the brain-action of children. According to the best authorities, the most rapid increase in the growth of the brain takes place before seven years of age; and it must be remembered that the crowns of all the permanent teeth, with the exception of the third molars, are simultaneously in the course of development with this great advance in the size of the brain. May we not, therefore, reasonably suppose that through the diminished vitality consequent upon this diversion of the formative energy from the teeth, by premature mental exertion, these organs necessarily become degenerated, and that this circumstance constitutes one great difference between the teeth of the intellectual and those of the uncultivated families of mankind?"

The argument from this universally recognized condition is this: During the formative and eruptive periods of the permanent teeth they are under the influence of an independent and peculiar vital (nervous) force; this innervation pushes on their development regardless of the more tardy growth of the osseous system; being implanted in a crowded position, in undeveloped maxillæ, they never have an opportunity to recover from it, and emerge in the same disordered arrangements in which the crowns were formed. In these positions, when fully erupted and surrounded by their alveolar walls, they become fixed regardless of any subsequent growth of the jaw; for it is one of nature's laws that, when the climax of development has been reached and the type is complete, function ceases. Under such circumstances it

ORIGIN OF INHARMONIOUS DEVELOPMENT.

23

would not be expected that any or all organic changes in the nerve-center would manifest the same results in detail; a disturbance of function would produce general results, the details of which might vary in every case. That such a lesion or innervation could only operate upon the permanent teeth is easily seen, when it is remembered that, to produce any marked effect upon the deciduous teeth, we should have to go back to intra-uterine life for the period of its influence, and before the child had an independent and sentient being.

This hypothesis does not find any contradiction in our daily observation; for such a disturbance of nerve-function might occur only for a limited period, and no other exhibition or evidence of it ever again appear.

The logical result of such reasoning would be that in individuals and families of sluggish or feeble intellects and phlegmatic temperaments, but with good physique, we should find capacious jaws and teeth not crowded. If a precocious or stimulated brain in infancy urges on and crowds the dental organs in advance of the growth of the jaws, then a brain of low caliber, or power, will be likely to have associated with it a retarded dentition, but with abundance of room. The grounds for such a conclusion are not merely theoretical, but are the results of observations in private practice for more than a quarter of a century in connection with investigations of different classes, nations, and races, ancient and modern, including all ranks and conditions of life from the highest order of intelligence down to the idiotic.

A perfect dental development is the result of well-balanced physical and nervous systems, without hereditary taint.

The causes of irregularities we classify as developmental and accidental; the developmental operating prior to the eruption of the teeth, and the accidental subsequently.

Abnormalities of development having their origin in the same individual are due to a disturbance of the trigeminal nerve during the period in which the crowns of the permanent teeth are forming and arranging themselves in the jaw

24

CAUSES OF IRREGULARITIES.

prior to eruption; or, when arising from causes antedating the life of the individual, are traceable to an inherited tendency, which tendency had its origin in a like disturbance in one of the progenitors, and was subsequently transmitted; or are the result of mixing different and distinctly marked types of jaws and teeth by the progenitors.

This proposition may be stated in another form as follows: The cause of irregularities of the teeth other than accidental lies in a want of development of the jaws commensurate with the size of the teeth; and this want of relation is sometimes due to a retarded growth of the jaw while the development and eruption of the teeth is not retarded, and sometimes due to the inheritance of large teeth out of all proportion to the size of the inherited jaw.

In our view we do not call a feeble mind, a sluggish brain, or a dull intellect a nerve-lesion or a brain-disturbance; for it is abundantly proved that when this condition is associated with an average physique, the development of the dental organs is tardy, but in regular order.

We have before us, then, both the solution of the problem and the evidence of most alarming symptoms in the physical and mental condition of the inhabitants of the centers of civilization.

There can be no question that the Creator intended that there should be perfect harmony in the development of the physical and nervous systems, and that where such harmony exists we come nearest to the standard of a perfect organization. This harmony of organization or true balance of the two systems demands that in the earlier years of life the brain and the nervous system be held in abeyance to the physical.

The healthier mental organization is of slower growth. If, therefore, we find that a certain mode of life destroys this harmony, breaks up this balance, there will follow necessarily deterioration and destruction of the race; and this is based on a well-recognized physiological law: if the brain and the

IRREGULARITIES PREVENTED.

25

nervous system are in an undue state of activity, the drain upon the sources of nutrition will be at the expense of the physique.

No force operating on the brain can interrupt or alter the type or inherited model of the dental arch, after the first decade of life. All cerebral disturbances occurring during that period, showing mental aberration, we should class under the head of idiocy imbecility. After that period, such manifestations come more properly under the head of lunacy—insanity—which might degenerate into imbecility or idiocy. Consequently, neither lunacy nor insanity, in the ordinary acceptation of the terms, can have any direct bearing upon the development of the dental organs; but such a condition would be most potent of evil if transmitted to offspring.

I do not hesitate to place it upon record that the next generation will see more of abnormality in dental development, and an increase of nervous and cerebral diseases, and that the two are correlated and spring from the same cause. It is too late to stop it in those who have passed infancy, but it is not too late to modify and partially remedy the evil in those now being born, and those who may be begotten hereafter.

To fathers and mothers surrounded by luxury and flattered with the precocity of their infants, which they are stimulating to the last degree, we say : Do not under peril encourage this brilliancy, which is now so charming; let the mind stagnate rather. For the first seven years of life give concern only to his morals and to his physique. Nourish him as you would nourish an animal from which you desired the finest development, stimulating only his moral nature, and his intellect will take care of itself. Thus, if he have no hereditary taint, will be laid the foundation of a splendid specimen of his race.

CHAPTER II.

CORRELATION OF IRREGULARITIES TO IDIOCY.

A FEW years since, Dr. Langdon Down, physician to the Earlswood Asylum for Idiots near London, reported the results of his investigations into the dental development of nearly a thousand feeble-minded youths who had come under his observations. His examination satisfied him that there was always narrowing between the posterior bicuspids of the two sides and inordinate vaulting of the palate; the only exceptions being certain macrocephalic idiots, in whom the mouth like the rest of the cranium was extraordinarily large. In a paper read before the Odontological Society of Great Britain, he says:

"A marked character of the teeth of idiots is their irregularity as to position. They are often crowded, so crowded as to present their sides instead of their anterior surfaces. They are often arranged on different planes. The canine teeth are frequently unduly prominent, and a marked sulcus is sometimes seen between the incisors and canines, with prominence of the incisors.

"Of the most significant value, however, is the condition of the palate. I have made a very large number of careful measurements of the mouths of the congenitally feebleminded and of intelligent persons of the same age, with the result of indicating, with some few exceptions, a markedly diminished width between the posterior bicuspids of the two sides. . . .

"One result, or rather one accompaniment, of this nar