Slide DMS51 [Fetal pig head]. Primitive mesenchyme is the embryological tissue from which all types of supporting connective tissue, including the skeleton, are derived. Study mesenchyme in this slide. This tissue is best seen in the area between the skin and the developing cranium. Note the fusiform or stellate shape of these undifferentiated cells and the apparent high ratio of nuclear to cytoplasmic volume. Surrounding intercellular material consists of sparse, delicate collagen fibrils and a viscous, amorphous ground substance, neither of which can be seen well in this routine type of preparation.