[Volume of the spine in the post-somite stage: morphometric quantification]

The volume of the spine was measured in 9 embryos from 8 to 31 mm Crown-Rump length (complete series of cross-sections). Spine morphometry was performed by planimetric point counting of horizontal projection on a 5 mm square grid. Total spine volume was integrated by multiplication of the thickness by the area. The integrated volumes (including the base of the skull around the foramen magnum) were aligned on the diagram : linear length v.s. semi-logarithmic volume. The correlation between the spine volume and the total length is very high (r = 0.94; p less than 0.01). There was no significant variation of the whole spine curvature during this period (angular value and curve radius). Linear measurements of the maximal width on the entire embryos and their spine were expressed with the crown-rump length, drawing linear curvatures with slight irregularity, emphasized by plotting the values of indices. These variations could be due both to the imprecision in section thickness and to the individual variation during the spinal growth for this embryonic phase.