FACIAL SKULL (See Moro, Diseases of the Mouth Cavity; Congenital Defects, vol.
In order to explain the fissures and defects in the area of the facial skull it is necessary to go back to that period of development in which they are still physiological. They are all remnants of primitive fissures. Why they have failed to close and whether there was a mechanical or pathological impediment, or whether insufficient power of ment was the cause, are questions which touch upon the origin of life. As a matter of fact, IIiinecke, by pairing young rabbits and also rachitie animals, was able to cause these fissures in the offspring. The same result occurred in children of chronic alcoholics. Degeneration and disturbed development deprive the organism of the power to normally complete the embryonal struc ture. This theory opens up a larger perspective in explanation of these phenomena than all the other theories taken together; at the same time there is no need to altogether discard the previous ones.
There is no doubt that increased intracranial pressure may lead to a fissuration in the facial skull just as well as a protruding cerebral hernia may lead to a cranial fissure. Brain tumors (Broca, Lannelonge),
amniotic cords, adhesions, insufficient amnion, are usually stated as causes, but the demonstrated heredity of these deformities (Fritsch; Haug) rather favors the first mentioned etiology.
Normally, a four-weeks embryo has a dome-like cranial vault (kopf kappe), t he anterior lower margin of which (frontal process) is bordered by the primary buccal cavity. The first branchial arches grow from both sides, uniting later to form the lower jaw. Somewhat higher up two other clefts, the upper maxillary processes, grow towards the fore head and are destined to form later the upper maxillary bone by union with the anterior margins of the head-fold. The anterior-inferior end of the head-fold likewise consists of several lobular formations which participate in the structure of the nose and the intermaxillary bone. There is no complete uniformity of opinion as to the participation of the various clefts in the formation of later organs (Kiilliker, Albrecht). A system of primary furrows develops between these sprouts the persist ence of which explains later congenital fissures.