The below is from an essay written by Ralph Waldo Emerson.

In the underlined part can you tell me what is the subject?

At a glance, it seems "In sickness, in fatigue," is a subject because of its position.

But I'm not sure. Can you help me?

The least activity of the intellectual powers redeems us in a degree from the conditions of time. In sickness, in fatigue, give us a strain of poetry or a profound sentence, and we are refreshed; or produce a volume of Plato or Shakespeare, or remind us of their names, and instantly we come into a feeling of longevity.
give is an imperative; the implied subject is "you".

Give us a strain of poetry, and we are refreshed

~

If you give us a strain of poetry, we [are / will be] refreshed.

~

If we are given a strain of poetry, we [are / will be] refreshed.

The same pattern occurs again after the underlined portion.

______________

This is a grammatical pattern worth learning. It is equivalent to an if ... then ... structure.

Try this cookie, and you will like it.

Take a step closer, and I will shoot.

Visit Paris, and your life will be changed.

CJ
Thanks, CJ. Thanks as always.