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produce what Rathke has called visceral arches. The superior maxillary bones, the lower jaw, and

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Mouth of the Embryo at the 38th day. a. Median bud.

1*. Superior maxillary bones. C C. Incisor buds.

2, 3, and 4. Second, third, and d d. Nostrils.

fourth visceral arches. The eyes.

6. Septum of the nose. b. The mouth.

7. The tongue. 1. The lower jaw.

8. Roof of the mouth.

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two of the bones of the ear are developed from the first of these 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. Cleft palate may indirectly throw some light upon the physiology of this subject, if we remember that the cleft is invariably at the back of the palate, except in cases of association with hare-lip; thus leading to the conclusion that union of the two halves of the upper jaw takes place from before backwards, and not uniformly in their entire length; for if the latter were the case, we might naturally expect to find an occasional instance of perforation of some part of the palate in the region lying between the alveolar ridge and the

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of the uvula ; but we are not aware of any such case having ever been seen.

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 be; the distance between certain parts, such as the infra-orbital foramina and nasal processes of the upper maxillary bones, being taken as points for comparison with measurements from the same parts in the healthy new-born child.

Dr. John Smith, of Edinburgh, brought this matter prominently before the scientific world

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by reading a paper on “. Certain Points in the Morphology of Cleft Palate” at a meeting of the Royal Society of Edinburgh, and gave to the subject additional interest by his philosophical reflections on the connection between the measurements taken at birth and those obtained from the mouths of adult cases. Having taken the first bicuspid of each side as a point of measurement (as the least change takes place here from infancy to adult life), in the normal dental arch averaging from one and an eighth to one and a quarter of an inch, Dr. Smith gives the measurement of sixteen cases of congenital cleft palate, in the full-grown subject, which show an average width somewhat less than in the perfect formed jaw.

“In six cases where the intermaxillary bones seemed altogether absent-probably instances of double cleft where they had been removed by the surgeon, or where they had never been developed—

1 inch,

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1 case measured i of an inch,
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1} of an inch, giving an average measurement of between and s of an inch.

“In ten cases of simple cleft palate alone, or of cleft palate combined with only unilateral fissure,

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1 case measured to be of an inch,
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of an inch,
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1 inch,
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1} of an inch, giving an average measurement of of an inch."

Dr. Smith then goes on to say that it would thus appear that while in the infant there is abnormal separation, in the adult there occurs abnormal approximation of the parts on each side of the fissure, as in fig. 2. To a certain extent this

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approximation of parts may be fortuitous—a misdirection of growth, dependent upon the absence

of the mesial structures, while the superior maxilla is becoming, as age advances, elongated downwards by the expansion of the antrum.

But as the same approximation seems to occur even where only a partial fissure exists—the cleft being limited to the palate, while the maxillary arch is throughout complete—there is reason to conclude that it is in some measure to be considered as an effort on the part of nature towards reparation, or rather amelioration of the existing defect.

We had for some time previous to the reading of Dr. Smith's paper been attracted to the subject of which it treats in the latter portion, by a number of cases giving most marked evidence of this approximation in the region of the first and second bicuspids, though we had not thought to apply to it the idea of its being a natural effort to decrease the size of the cleft.

We came then to the conclusion, and have had no reason up to the present time to doubt its soundness, that it was rather owing to the eruption of the molars and the pressure they exerted than to any movement originating per se in the portion of the jaw indicated by the position of the bicuspids.

If the upper jaw be taken as representing an arch, it will, we think, be conceded that where the bicuspids are developed would be the weakest part of that arch, and supposing the central portion

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