Neonatal hematology: a historical overview

Ancient concepts of the blood were described by Hippocrates and Galen 2000 years ago in their doctrine of “humors.” It was believed that the body was made up of four humors – blood, phlegm, black bile, and yellow bile – and that these four componentshadthequalitiesofheat(“hot-blooded!”),cold, moist, and dry. The Galenic concept of the blood prevailed through the Middle Ages. Health or disease was a result of a balance or imbalance, respectively, between these humors, and this was the basis of the practice of therapeutic blood-letting (which, fortunately, was performed infrequently in children) through the mid nineteenth century as a way to rid the body of the abnormal humors believed to cause a wide variety of diseases. The hematology of the fetus and newborn is a relatively recent area of study whose development dependedupontheevolutionof thescienceofhematology and, especially, upon methods to study the blood and its elements. As Wintrobe has pointed out, the development of the field of hematology has been driven by technology. He divided the evolution of hematology into two general areas: morphology, which relied on the development ofmicroscopy, and quantitationof the elementsof theblood,whichcame later [1]. The invention of themicroscope enabled identification of the blood cells. Antonj van Leeuwenhoek, working in Delft, Holland, constructed a primitive microscope from aminute biconcave lens mounted between two metal plates attached to a screw that permitted focussing. Leeuwenhoek’s publication in 1674 contained the first accurate description of the red blood corpuscles [2]: