High school students are told that Pavlov taught dogs how to drool with a bell, because it sounds nice. In reality Pavlov drilled holes into dogs' stomachs and stuck a catheter in there through their abdominal walls, and measured the pH and enzyme content of gastric secretions when he rang the bell. Needless to say the dogs died after the experiment.
It can be exhilarating to know that common knowledge is wrong, and you know the truth, but in thin case, you are the one who is wrong. Pavlov did research on the digestive system, which used catheters as you described. However, when it came to his conditioning research, drooling was the quantitative result that was recorded. And he did use a bell, as well as other stimuli.