The lecturer had succeeded in devising experimental methods and
apparatus by which the plant was made to give an answering signal, which
was then automatically recorded into an intelligible script. The results
of the new investigations were so novel that Professor Bose spent
several years in perfecting automatic instruments which completely
eliminated all personal equations. The plant attached to the recording
apparatus was automatically excited by a stimulus absolutely constant,
making its own responsive records, going through its period of recovery,
and embarking on the same cycle over again without assistance at any
point from the observer. The most sensitive organ for perception of a
stimulus was the human tongue. An average European could by his tongue
detect an electrical current as feeble as six micro-amperes, a
micro-ampere being a millionth part of a unit of electrical current.
Professor Bose found that his Hindu peoples could detect a much feebler
current, namely, 1.5 micro-amperes. It was an open question whether such
a high excitability of the tongue was to be claimed as a distinct
advantage. But the fact might explain the eminence of his countrymen in
forensic domains! (Laughter.) The plant, when tested, was found to be
ten times more sensitive than a human being.