Heredity is an undoubted factor in their production, and an investigation of the family history will in many cases elicit a confirmation of such an idea. Thus in two instances in my own practice I have been able to determine that the father, grandmother, and great-grandfather had all suffered from harelip to a greater or less extent. Mason in his book mentions several other illustrations of this fact. Liston operated on four members of one family for harelip. M. Demarquay[31] related a case in the Surgical Society of Paris, in which, from the grandparents downwards, eleven children had been born with harelip. In the ‘British Medical Journal’[32] a correspondent related his own family history, stating that it had occurred in some branch or other for the past hundred years.
An examination of the parents’ mouths should always be made when possible, and very commonly it will be found that one or both possess a short upper lip, and a high arched narrow palate. In others there is a slight groove in the alveolar process between the central and lateral incisors. I have also observed a small symmetrical crease on either side of the median line in the upper lip, indicating a tendency to, if not a natural intra-uterine cure of, a double harelip.
In some instances the deformity dies out of families, possibly from the fact that the defective condition in one parent is remedied by a more perfect development in the other; whilst in others the tendency distinctly increases, and a father or a mother with harelip will beget a family where three out of the four or five children will be similarly affected. By a proper selection of mates this deformity could probably be bred out, as well as bred up to.
The so-called Maternal Impression is looked on, especially by the laity, as another common cause of these deformities. Medical men will usually receive histories of such with a smile of incredulity, and rightly so; but some recorded cases, if true, are so definite that to condemn such an explanation too dogmatically seems scarcely to indicate a scientific spirit. The usual type of history given is that after the mother has seen the defect in the newly-born infant, she looks back over the preceding nine months to see if there were any apparent cause for the trouble, and seeking out particularly some shock or fright produced by seeing something resembling the defect in her infant often selects something trivial and irrelevant. The following authentic case is worthy of mention:[33]
A child was born deformed by a left unilateral harelip. The mother immediately asked to see the infant, declaring she was afraid it was marked, and on seeing it manifested no surprise at the appearance of its lip, stating that when about four months pregnant she received a fright, from the shock of which she had not yet fully recovered. Startled by a boy running almost into her arms, from whose face blood was streaming, she had seen a cut in the left side of the upper lip, extending through its substance into the nostril, laying bare the gums and teeth. She turned faint with fright, and could not banish the thought even after reaching home. The lad was subsequently examined, and the scar of a cut was found in that position.
In spite of such facts, however, one hesitates somewhat in accepting the antecedent alarm and the subsequent deformity in the relationship of cause and effect. The imaginary “maternal impression” probably in nine cases out of ten has nothing to do with the defect; whilst a real “maternal shock” which possibly led to the production of the deformity passes unnoticed. Mr. Carless tells me of a case recently seen by him of a cleft of the soft palate in a child, whose mother, without asking any leading questions, gave a history of a sharp attack of febrile disturbance keeping her in bed two or three weeks at a period when the fœtus could not have been more than two months old. This is the type of maternal shock we should possibly look for, rather than the more out-of-the-way maternal impressions commonly suggested.
The union of the parts entering into the formation of the palate, alveolus, and lip is normally completed by the eighth to the tenth week, and when once this has occurred in these parts no maternal impression (such as seeing a gashed lip) could, as far as we know, bring about a retrogressive change. Should some shock occur to the mother prior to that period, we can fully appreciate the possibility of its interfering with the typical growth of the parts then being produced; and the fact that the due adjustment and union of so many component parts is requisite for the normal development of the mouth and face explains why these defects are relatively so common. That a severe shock to an infant may produce coincidently a lamellar cataract and defective development of dentine is well recognised; that a similar type of shock acting on the mother should result in defective union of parts developing at that period in the fœtus is not strange; but that the real shock and the so-called “Maternal Impression” are one and the same is more than doubtful.
CHAPTER II.
ANATOMY AND PHYSIOLOGY OF THE NORMAL PALATE.
The hard palate—The velum and its muscles—The mucous membrane—The blood supply—The shape and size of the hard palate—Functions.