Summary

Edmund Owen 1911 Encyclopædia Britannica, Volume 6… (1911)

Hare-lip is often associated with cleft palate. Though we are at present unable to explain why development should so frequently miss the mark in connexion with the formation of the lip and palate, it is unlikely that maternal impressions have anything to do with it. As a rule, the supposed “fright” comes long after the lips are developed. They are completely formed by the ninth week. Heredity has a powerful influence in many cases. The best time for operating on a hare-lip depends upon various circumstances.
Source: Wikisource

Edmund Owen 1911 Encyclopædia Britannica, Volume 6… (1911)

But, assuming that the infant is in fair health, that he is taking his food well and thriving on it, that he is not troubled by vomiting or diarrhoea, and that the hare-lip is not associated with a defective palate, the sooner it is operated on the better. It may be successfully done even within a few hours of birth. When a hare-lip is unassociated with cleft palate, the infant may possibly be enabled to take the breast within a short time of the gap being closed.
Source: Wikisource

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