Cohn was also selfless in the best (and worst) scientific tradition. For example, he would often give public demonstrations of the blood fractionation machine, in which he would fractionate his own blood on the stage during the lecture. In one such lecture, at the Instituto Superior Técnico in Lisbon, the machine became blocked (without Cohn's knowledge) and exploded, showering the first few rows of the audience with Cohn's blood. Cohn maintained his "sangfroid", however, and continued his lecture without significant interruption. More generally, Cohn drove himself relentlessly and ignored his doctors' advice to cut back on working because of his high blood pressure (which finally killed him).