5. Cervical Fissure (Fistula colli congenita).
Recent observations teach us that the ori ginal branchial fissures may persist in the neck even in adults. Hyrtl mentioned this malformation in a man of twenty, in whom the external cervical opening was small and com municated with the pharynx close to the epi glottis. Among 34,000 young men, Riecke found a Gtula colli congenita twice.
6. Fissure of the Face.
In order to obtain a correct notion of the different forms under which fissure of the face may occur, it will be necessary to know the gradual metamorphoses of the face during its developement. Originally there is a common oral and nasal cavity. The place of the nose is occupied by two fissures, which extend from the internal angles of the eyes to the superior margin of the oral cavity. There is at this period not the least indication of a palate, so that the mouth and the nose form one common cavity. In a human foetus of less than an inch in length, Meckel found the first rudiment of a palate, in the form of an arc or a horse-shoe shape. On each side this arc is gradually completed, so as to be at first open at its posterior part, hut closed afterwards, and forming a complete trans verse plate, separating the nasal from the oral cavity. Rathke examined this more in de tail, in foetuses of the sheep : — 1. He learned that the supermaxillary ca vity is formed on each side from the lateral walls of the cranium.
2. That between those two parts grows out of the frontal wall of the skull a third eminence, which forms the basis for the sep tum of the nose, that is, for the formation of the vomer, of the septum of the ethmoid bone, and of the intermaxillary bones.
3. That the two parts, quoted under No.1., are bent inwards, and coalesce with the mesial part.
4. That the nasal cavity is at first a groove, and has originally a form which persists through their whole life in fishes.
5. That the oral and the nasal cavity form originally a common cavity.
6. That the palate is originally a fissure. By arrest of developement in these different stages of embryogenesis, are formed the dif ferent species of facial fissure.
a. Complete fissure of the face.— The high est degree of malformation is, when the fissure is extended from the tingle of the mouth to the internal angle of the eye, the orbits, the nose, and the mouth forming but one cavity. J. S. Meckel, Van Doeveren, and myself have published examples of this malformation com plicated with acrania. The fissure sometimes extends only over one lateral part of the face (Leuckart), and in the greatest transition to the natural condition it is but a shallow groove, as is represented in fig. 596.
A fissure sometimes extends in a transverse direction over the head. C. Meyer observed this twice in new-born sheep. In both the palate had a double fissure, and the normal opening of the mouth reached as far as the ear, which in one of these lambs presented a trans verse fissure.
b. Double labiunz leporinum. — A transition to the normal condition, yet a very imper fect one, is when the fissure is not extended over the whole surface of the face, but is re stricted to the upper jaw. The highest de gree of deformity is double hare-lip with fissured palate (Labium leporinunz duplex cum palato fisso). On each side of the upper lip a fis sure extends from the angles of the mouth to the alw nasi. Between these is a protube rant tubercle, covered by a separate part of the upper lip, and consequently by the external skin and the gums. The tubercle is connected with the septum of the nose, generally obliquely distorted, and is filled up with the germs of the incisors. By the confusion of the oral and nasal cavities, the true nasal ori fices are wanting, the osseous palate is defec tive, the soft palate and the uvula are fissured, and the vomer united anteriorly with the pro tuberance, hangs in the midst of the fissure. In a lesser degree of malformation, the alveolar margin of the upper jaw is alone fissured, and in the least degree the palate is complete.