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Webster 1913 Edition

Noun.

Lack of activity or exertion; inertness; quietude.

[R.]

These vicissitudes of exertion and

inertion

of the arterial system constitute the paroxysms of remittent fever.

E. Darwin.

Noun.

Want of activity; want of action or exertion.

These vicissitudes of exertion and inertion of the arterial system, constitute the paroxysms of remittent fever.

inertion ‎(uncountable)

Want of activity or exertion; inertness; quietude.
These vicissitudes of exertion and inertion of the arterial system constitute the paroxysms of remittent fever. — E. Darwin.