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Carnegie Stage 15 Introduction

Stage 15 embryos have a greatest length of 7 to 9 mm and an estimated postfertilization age of 36 days.  The lens vesicle, nasal pit and hand plate are present and the future cerebral hemisphere is distinct.  The stage is represented by Carnegie embryo #721 that had a grade of excellent but more recently was downgraded to good. It is one of the best specimens in the Carnegie collection at this stage.  It has a greatest length of 9.0 mm (after fixation) and is median within the stage.

The embryo was prepared for microscopic examination in 1913. It was fixed in Zenker's formol, embedded in paraffin and serially sectioned transverse to the long axis at 15 microns. The sections were mounted on 27 large glass slides and stained with hematoxylin and eosin. There are 558 sections through the embryo.

The Browse part of the database includes 135 of the 558 section images. Approximately every fourth section image was digitally restored and labeled, and can be viewed at four magnifications (only 3 zoom levels are available on the CD version). Several 3D reconstructions were produced from the aligned section images. Animations of the 3D reconstructions of the embryo surface and fly-through animations of the aligned section images are also included on the disks.

There are few published accounts of this specimen. Included on the disk are a few photographs of the embryo before it was sectioned.


Source: The Virtual Human Embryo.