Published online by Cambridge University Press: 06 July 2012
Our knowledge of the earliest stages of blood-vascular development in the human embryo suffers from a dearth of suitable material. Early human specimens are not frequently available for examination; many are pathological; some, although of value for other purposes, are not sufficiently well preserved to furnish observations on angiogenesis; direct microscopic observation of the tissues while undergoing development cannot be carried out as is possible, say, in the chick embryo. Our knowledge of the process must be based on descriptions of separate specimens representing different stages. Individual specimens, therefore, are worthy of careful record.