_Reflex actions_ Reflex actions, in the strict sense of the term, are
due to the excitement of a peripheral nerve, which transmits its
influence to certain nerve-cells, and these in their turn excite
certain muscles or glands into action; and all this may take place
without any sensation or consciousness on our part, though often thus
accompanied. As many reflex actions are highly expressive, the subject
must here be noticed at some little length. We shall also see that some
of them graduate into, and can hardly be distinguished from actions
which have arisen through habit?[109] Coughing and sneezing are
familiar instances of reflex actions. With infants the first act of
respiration is often a sneeze, although this requires the co-ordinated
movement of numerous muscles. Respiration is partly voluntary, but
mainly reflex, and is performed in the most natural and best manner
without the interference of the will. A vast number of complex
movements are reflex. As good an instance as can be given is the
often-quoted one of a decapitated frog, which cannot of course feel,
and cannot consciously perform, any movement. Yet if a drop of acid be
placed on the lower surface of the thigh of a frog in this state, it
will rub off the drop with the upper surface of the foot of the same
leg. If this foot be cut off, it cannot thus act. After some fruitless
efforts, therefore, it gives up trying in that way, seems restless, as
though, says Pfluger, it was seeking some other way, and at last it
makes use of the foot of the other leg and succeeds in rubbing off the
acid. Notably we have here not merely contractions of muscles, but
combined and harmonized contractions in due sequence for a special
purpose. These are actions that have all the appearance of being guided
by intelligence and instigated by will in an animal, the recognized
organ of whose intelligence and will has been removed. [110]
We see the difference between reflex and voluntary movements in very
young children not being able to perform, as I am informed by Sir Henry
Holland, certain acts somewhat analogous to those of sneezing and
coughing, namely, in their not being able to blow their noses (_i.e._
to compress the nose and blow violently through the passage), and in
their not being able to clear their throats of phlegm. They have to
learn to perform these acts, yet they are performed by us, when a
little older, almost as easily as reflex actions. Sneezing and
coughing, however, can be controlled by the will only partially or not
at all; whilst the clearing the throat and blowing the nose are
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