The subdivisions of the neural folds in man

Abstract

Institufion of Washington SIX FIGURESVeit and Esch have recently given us the most complete and detailed study of a vertebrate embryo during the period of somite formation that has ever appeared. 911 the labor and study expended upon it has been well worth while, as human embryos of this period are very rare. The specimen is certainly normal and the preservation above reproach. The embryo has eight somites and belongs to the beginning of the third week, a period which Prof. H. M. Evans and I have been studying for some years. Most of Veit and Esch's findings fit well into the sequence of events as we have interpreted it from our series of embryos. There is, however, a radical disagreement, in our interpretations of the nervous system, and in view of the great importance of the Veit embryo to human embryology, it would seem wise to call attention to the matter.In his first paper based upon this embryo ('18), as well as in the complete description ('22) Veit has adopted a slight modification of the traditional interpretation of the nervous system in young human embryos. This seems to have originated with Kollmann ('89) in his description of the celebrated embryo ' Bulle,' which he had studied simply as a whole mount in balsam.The identification of the regions of the brain was, in the nature of the case, almost wholly subjective. The subsequent writers who have ventured interpretations of the nervous system of embryos younger than 'Bulle' h m e followed Kollmann more or less closely. They have all made the forebrain relatively enormous and the hindbrain insignificant in size. None of these workers 23 1

Inherited diseases of the inner ear in man in the light of studies on the mouse.

“…The alternative hypothesis would be that the melanocytes themselves in some way affect the inner ear, but no evidence can be found in its support. The presence of some normal neural epithelium in the cochlea with the resulting lack of total deafness in piebaldlethal mice, and the non-involvement of the vestibular part, may be ascribed to the dual origin of the acoustic ganglion, for there is much evidence that it originates in the otic placode (Campenhout, 1935;Yntema, 1937;Halley, 1955;Batten, 1958) as well as in the neural crest (Bartelmez, 1923;Adelmann, 1925). Other possible explanations of the same phenomenon have been given elsewhere (Deol, 1967).…”

The development of the neural crest in the human

“…Originally the mass so designated was thought to give rise to the geniculate and vestibulocochlear ganglia (e.g. Bartelmez, 1923; Bartelmez & Evans, 1926, in the human). Subsequently, however, the so‐called acousticofacial crest of mammals is generally believed to be purely facial.…”

Patterns of cell division and interkinetic nuclear migration in the chick embryo hindbrain

“…The primary events in generating the rhombomeric pattern might be expected to involve specific patterns of cell division, and changes in the abun-dance and distribution of cytoskeletal elements. Neuromeres were first proposed to arise by rapid forward growth and localised expansion (Adelmann, 1925 ), preceded by local proliferation within the neuroepithelium (Bartelmez, 1923;Bartelmez and Evans, 1926). Such proliferation centres were later shown to be related to the position of the neuromeres (Kallkn, 1953).…”