Final answer:
The type of bilirubin in physiologic jaundice is indirect bilirubin, or unconjugated bilirubin, which accumulates when the liver is unable to conjugate it efficiently.
Step-by-step explanation:
The type of bilirubin in physiologic jaundice is indirect bilirubin, also known as unconjugated bilirubin. Physiologic jaundice commonly occurs in newborns and is a result of the immature liver's inability to process and conjugate the bilirubin efficiently. Bilirubin is a byproduct of the breakdown of red blood cells, and in physiologic jaundice, there is an accumulation of unconjugated bilirubin, which is not water-soluble and therefore cannot be excreted easily.
Unconjugated bilirubin must be transported to the liver, where it is conjugated with glucuronic acid to form conjugated bilirubin, which is water-soluble and can be excreted in the bile. When the liver is unable to perform this process efficiently, the levels of unconjugated bilirubin rise, leading to jaundice. This elevated level of unconjugated bilirubin can be measured by the indirect Van Den Bergh test, where unconjugated bilirubin does not react with the Diazo reagent unless alcohol is added, resulting in a purple-red color.