Universlty of Manitoba, ln Partîal Fulfiìlment - MSpace at the ...

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serîal sectlonlng a camera lucida drawi.ng was made of every embryo.
4.6.2 Problems in Examlnation
Examlnation.of these early embryos presented severê'l problems:
a) Staging by somîte counts was not always easy because of necrosis or
cyst-formatlon in the somite regíons, and torsôon or opacity of older
embryos
b) the same processes often involved the neural folds, making assessment
of neural closure diffîcult
even death was not always obvious because some embryos showed
")
excessîve. necrosís when still alive, whereas other embryos without a beating
heart mîght be well-preserved though technically dead.
\.7 EXAMtNATIoN oF oLDER EMBRYoS
defects.
0lder embryos were fixed in Carnoyrs fluid and exdmlned for external
\.7.1 F ive Day Embryos
'
Some embryos were recovered at a totâl of fíve days incubation, with
the externâl configuration establ ished but well before the second peak of
embryonic mortal ity (Hamilton, 19!2).
\.7.2 Eleven - Twelve Day Embryo:
To correlate skeletal defects of the spine with spinal cord lesions,
however, a further period of development was necessary, "f,i"t'
resulted in
further mortal ity. As windowing produced some growth retardêtion, experîmenta¡
embryos were recovered at twelve days and control embryos at èleven
days of total incubation. After examination and measurement of all open
neural defects, the cartîlaginous skeleton was stained with alcian blue
(O;eda et al, 1970) and the embryos cleâred ln xylol and benzyl benzoate