ions in allied fields. Nevertheless, a
full decade elapsed before another discovery of comparable importance
was made. Then Marshall Hall, the most famous of English physicians
of his day, made his classical observations on the phenomena
that henceforth were to be known as reflex action. In 1832, while
experimenting one day with a decapitated newt, he observed that the
headless creature's limbs would contract in direct response to certain
stimuli. Such a response could no longer be secured if the spinal
nerves supplying a part were severed. Hence it was clear that responsive
centres exist in the spinal cord capable of receiving a sensory message
and of transmitting a motor impulse in reply--a function hitherto
supposed to be reserved for the brain. Further studies went to show that
such phenomena of reflex action on the part of centres lying outside the
range of consciousness, both in the spinal cord and in the brain itself,
are extremely common; that, in short, they enter constantly into the
activities of every living organism and have a most important share in
the sum total of vital movements. Hence, Hall's discovery must always
stand as one of the great mile-stones of the advance of neurological
science.

Hall gave an admirably clear and interesting account of his experiments
and conclusions in a paper before the Royal Society, "On the Reflex
Functions of the Medulla Oblongata and the Medulla Spinalis," from
which, as published in the Transactions of the society for 1833, we may
quote at some length:

"In the entire animal, sensation and voluntary motion, functions of
the cerebrum, combine with the functions of the medulla oblongata and
medulla spinalis, and may therefore render it difficult or impossible to
determine those which are peculiar to each; if, in an animal deprived
of the brain, the spinal marrow or the nerves supplying the muscles be
stimulated, those muscles, whether voluntary or respiratory, are equally
thrown into contraction, and, it may be added, equally in the complete
and in the mutilated animal; and, in the case of the nerves, equally in
limbs connected with and detached from the spinal marrow.

"The operation of all these various causes may be designated centric, as
taking place AT, or at least in a direction FROM, central parts of the
nervous system. But there is another function the phenomena of which
are of a totally different order and obey totally different laws, being
excited by causes