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6.3.10 SequenJ¡¿il ll lúSti¡it¡on6 óf Sèléctéd Eríbryos
To ¡l lustrate the events of normal and abnormal neural closure a group
of. sequent¡al. drawìngs of every tenth section are presented for eight
embryos. Serlal sections under a Leltz Dialux microscrope were projected
through a Sony DXC-1650 camera onto a Sony PYJ fO¡O micro-vìdeo monitor
and traced at an in¡tial magnifîcation of x88. Embryos selected for
illustration are shown ln Table J4 and Fiç.95to 102.
TABLE 34.
SEOUENTIAL ILLUSTRATI ONS
Embryo Stage Neural Ti ssue
18C 4 lt+ elevated (normal) posterior rhomboíd sinus
6f 34 1l+ everted (abnormal) posterior rhomboid sínus
18C 27 13+ normal neural closure
18E 36 14+ early myeloschlsis
\28 8 17 later myeloschlsîs
3OC 22 16 normal _neural closure
3OE 76 16 early hemimyel ia
428 50 18 larer hemlmyelia
At Stâge. 1l+ non-closure of the neural plate is first manifest as
eversion of the neural folds (68 34,Fîg.96 ) rather than elevation
(18C 4iFig.95 ) at the posterior rhomboîd sinus. Neither embryo shows
an overlap zone.
slightly later, a control embryo (18C 27,Fis,97 ) shows the neural
canaì traceable down to en open neural plate overlyîng one accessory
canal at the poster¡or rhomboid sinus. ln a comparable embryo with
early myeloschisis (l8e 36,Fig. 9B ) an open lrregular neural plate