In a study shortly to be completed, the subject of the variation in inorganic phosphorus content of the blood of the new-born at different seasons of the year has been investigated. For the purpose of determining this seasonal variation, the blood of the umbilical cord was used as the index of the infant's blood as a whole.
Most investigators1 have used cord blood as representative of the infant's blood. Anatomically considered, it is an integral part of the fetal circulation, and the umbilical vein is the ultimate continuation of the umbilical arteries.
As differences appeared when blood from other sources in the fetal circulation was examined and compared with cord blood, the question arose as to whether cord blood was a true index of the infant's blood, and, furthermore, whether a substance such as Wharton's jelly would contribute to its fluid content thus diluting the blood and rendering its