Another familiar story is:
XCVII. THE DOCTOR'S APPRENTICE.
ONCE upon a time there was a doctor who took his apprentice with him when he made his visits. One day while visiting a patient, the doctor said: "Why do you not listen to my orders that you are not to eat anything?" The invalid said: "Sir, I assure you that I have eaten nothing." "That is not true," answered the doctor, "for I have found your pulse beating like that of a person who has eaten grapes." The patient, convicted, said: "It is true that I have eaten some grapes; but it was only a little bunch." "Very well; do not risk eating again, and don't think you can fool me."
The poor apprentice, who was with the doctor, was amazed to see how his master guessed from the pulse that his patient had eaten grapes; and as soon as they had left the house he asked: "Master, how did you perceive that he had eaten grapes?" "Listen," said the doctor. "A person who visits the sick must never pass for a fool. As soon as you enter, cast your eyes on the bed and under the bed, too, and from the crumbs that you see you can guess what the patient has eaten. I saw the stalk of the grapes, and from that I inferred that he had eaten grapes."
The next day there were many patients in the town, and the doctor, not being able to visit them all, sent his apprentice to visit a few. Among others, the apprentice went to see the man who had eaten the grapes; and wishing to play the part of an expert like his master, to show that he was a skilful physician, when he perceived that there were bits of straw under the bed, said angrily: "Will you not understand that you must not eat?" The invalid said: "I assure you that I have not even tasted a drop of water." "Yes, sir, you have," answered the apprentice; "you have been eating straw, for I see the bits under the bed." The sick man replied at once: "Do you take me for an ass like yourself?" And so the apprentice cut the figure of the fool that he was. 
 Pitrè, No. 180. A literary version is in Straparola, VIII. 6. For other references see Schmidt, Straparola, p. 329; and Oesterley's notes to Pauli's Schimpf und Ernst, No. 357.
Doctor's Apprentice, The
Italian Popular Tales
Crane, Thomas Frederick
Houghton Mifflin and Company
Year of Publication:
Country of Origin:
ATU 1862C: Diagnosis by Observation