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MICROSCOPICAL INVESTIGATION. 363
had admitted independent irritability only for the muscular
tissue of the heart and intestine. It was established
by experiments on frogs and tortoises that power of
movement exists after removal of the brain. STENO drew
attention to the part played by the blood in muscular
action; he ligatured the descending aorta in the frog, and
showed that paralysis of the muscles of the posterior part
of the body ensues. BAGLIVI also sought for the cause of
the inherent contractility of muscular tissue in the blood,
and considered the nerves to be only the exciters of move­
ment; and he made on this occasion certain remarks which
may be taken as alluding to the distinction between plain
and transversely striated muscular fibres* MAYOW, on
the other hand, attached great importance to the influence
of the atmospheric air upon the activity of muscle. GLISSON
regarded irritability as a propertyf belonging to matter in
general; WlLLlS considered it to belong only to muscles.
Afterwards A. HALLER, as the result of a great number
of researches and vivisections, established on a firm basis
the different degrees of sensibility and irritability possessed
by the various tissues and organs of the body. He came
to the conclusion that sensibility is associated with the
existence of nerves and irritability with that of muscular
tissue.
The nerves were held to be filled with a fluid, and
GLISSON even spoke of currents flowing to and fro in
nerves. Clearly, these have only the name in common
with those electrical currents which at the present day are
known to manifest themselves in nerves. In the explana­
tion of the action of nerve force the Iatrophysicists and
the Iatrochemists were opposed to one another ; for while
the former, with NEWTON, assumed the presence of vibra­
tions, of tensions, and relaxations, the latter considered
* G. BAGLIVI: De fibra motrice et morbosa in his Opera omnia medicopract.
et anatom., Antwerpen 1719.
f GLISSON: De ventriculo et intestinis, Amstelod. 1677, p. 168 et seq.
according to G. H. MEYER in HAESER'S Archiv, Jena 1843, v > P- 1 et seq.