Reason behind the Kindness?

Specialist is giving bedside teaching to a group of medical students.At a patient's bedside,Specialist: "This patient has very interesting heart murmur. You all can take turn to listen to it," He then put his stethoscope diaphragm at the valve area, and passes the earpiece to one of the students.So the students took turn to listen to it. The last student, after listening, took out an alcohol swab