new subject with details that cannot be more than referred to
here. But the crowning achievement of the period in this direction was
the discovery made by the German, J. L. Schoenlein, in 1839, that a very
common and most distressing disease of the scalp, known as favus,
is really due to the presence and growth on the scalp of a vegetable
organism of microscopic size. Thus it was made clear that not merely
animal but also vegetable organisms of obscure, microscopic species have
causal relations to the diseases with which mankind is afflicted. This
knowledge of the parasites was another long step in the direction of
scientific medical knowledge; but the heights to which this knowledge
led were not to be scaled, or even recognized, until another generation
of workers had entered the field.

PAINLESS SURGERY

Meantime, in quite another field of medicine, events were developing
which led presently to a revelation of greater immediate importance to
humanity than any other discovery that had come in the century,
perhaps in any field of science whatever. This was the discovery of
the pain-dispelling power of the vapor of sulphuric ether inhaled by a
patient undergoing a surgical operation. This discovery came solely out
of America, and it stands curiously isolated, since apparently no minds
in any other country were trending towards it even vaguely. Davy, in
England, had indeed originated the method of medication by inhalation,
and earned out some most interesting experiments fifty years earlier,
and it was doubtless his experiments with nitrous oxide gas that gave
the clew to one of the American investigators; but this was the sole
contribution of preceding generations to the subject, and since the
beginning of the century, when Davy turned his attention to other
matters, no one had made the slightest advance along the same line until
an American dentist renewed the investigation.

In view of the sequel, Davy's experiments merit full attention. Here is
his own account of them, as written in 1799:

"Immediately after a journey of one hundred and twenty-six miles,
in which I had no sleep the preceding night, being much exhausted, I
respired seven quarts of nitrous oxide gas for near three minutes. It
produced the usual pleasurable effects and slight muscular motion. I
continued exhilarated for some minutes afterwards, but in half an hour
found myself neither more nor less exhausted than before the experiment.
I had a gr