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The favourable reception of the first Edition of this work by the Medical Press and Profession, both in England and America, has shown that it was not altogether an unnecessary contribution to Dental literature.

The alterations and additions I have now made will, I trust, render it not less worthy of the considerate notice with which it has been already received.

I cannot but express my deep obligations to my friends, Dr. Morell-Mackenzie and Mr. Christopher Heath, for their great kindness in placing cases and preparations at my disposal, during the progress of this second Edition through the press.

In the former Edition of this Work I enjoyed the co-operation of Mr. Robert Ramsay, but being no longer connected with that gentleman, I am alone responsible for the present volume.

81, WIMPOLE STREET, CAVENDISH SQUARE, W.

May, 1870.

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CHAPTER I.

ON THE ORIGIN AND DEVELOPMENT OF CLEFT PALATE.

THE predisposing causes of cleft palate have often been a matter of careful research and reflection; but up to the present time no satisfactory reason has been given for the development of this deformity. It has occasioned great speculation and conjecture, but we cannot affirm that we are any nearer the truth now than we were many years ago. That it is in some instances caused by arrested development, the want of substance in the parts would seem to indicate; but in others it is apparently more from a want of union in the median line at the proper time than from any lack of material to produce the perfect palate, since the margins of the cleft in many cases supply more than enough to fill up the deficiency in the operation of staphyloraphy, while in others again no amount of skill would be able to bring the opposite sides into such contact as to get permanent union. This variety would then appear to point to the fact, that while in some cases

the lesion may occur from arrested development during the whole time of pregnancy, in others it occurs only at that time when the parts should unite in the central portions, this condition being consequent, according to Dr. Engel's opinion, to increased breadth of the anterior portion of the head, which is again caused by a variety of conditions in embryonic life, such as congenital hernia cerebri, dropsy of the third ventricle, or of the anterior cornua of the lateral ventricles, or excessive development of the anterior cerebral lobes.

This view of the case becomes the more intelligible if we refer to the statements of embryologists as to the condition of the embryo about the thirty-eighth day.

The annexed woodcut, copied from the work of M. Coste, shows the manner in which the parts ultimately producing the cavity of the mouth and the adjacent structures are developed.

The superior maxillary bones, the lower jaw, and two of the bones of the ear are developed from the first of a series of arches, the two halves of which are separated by a space immediately below the frontal eminence.

The jaws being thus developed in two segments, meeting in the median portion under natural circumstances, and the central portion of the lip being developed from a separate part to that of each side, we can readily understand how the

arrest of development of any of these parts for ever so brief a time at this period of embryonic life would lead to great deformity.

In consequence of the distension within the cranium of the embryo, the parts on each side of the palatal fissure appear to be not only deficient in the median line, but more widely separated than under the natural condition they would