While instructing his pupils in grammar, a country school-teacher gave
out this sentence to be parsed: "Mary milks the cow." Each word had been
parsed except the last, which fell to Bob, a sixteen-year-old boy, near
the foot of the class, who began thus:
"Cow is a noun, feminine gender, singular number, third person, and
stands for Mary."
"Stands for Mary!" said the astonished teacher. "And, pray, Robert, how
do you make that out?"
"Because," answered the hopeful pupil, "if the cow didn't stand for
Mary, how could Mary milk the cow?"