Most embryologists will say after Thoma, that bloodvessels follow the pattern set by organs and have no influence on organs in themselves. If this be true in normal development, what would we find in abnormality? If there be a certain vascular pattern in the developing face, will this pattern be essentially different in cases of clefts of primary and secondary palate? Or is Thomas statement also true here, and are the differences due to following the abnormal formation of the nasal and maxillary parts of the face? Could it be so that the unknown agents responsible for abnormal development act...