What does it mean when different physicians disagree about a diagnosis? I am joined by Dr. Shani Herzig as we explore this issue in the second part of my series on the development of diagnosis. We’re going to discuss the advent of signal detection theory in the middle of the 20th century as new diagnostics such as laboratory testing and x-rays started to challenge the classical view of diagnosis. Along the way, we’re going to talk about focal infection theory and why it seems that everyone in older generations had their tonsils removed as children, early and very inefficient chest x-rays, British radar operators trying to figure out if they were looking at a flock of geese or a German bomber, and finally probably one of the most important people in medical diagnostics that you’ve never heard of -- Jacob Yerushalmy.   If you want to purchase any Bedside Rounds swag, the store is at https://www.teepublic.com/stores/bedsiderounds.