Thank you, misterakpan, I didn't think to do the citations. In any case, this was from a lecture that I gave to my students in Laboratory Analysis back in 1990 while I was an Adjunct Professor at PCSC in Philadelphia. I wrote this off the top of my head, but I guess I could scratch up the citations, if I had to. I'm glad someone is reading this post; most of medical history is a mystery to many and will be lost if not re-iterated every once in a while!