A scientist is nearly assassinated. In order to save him, a submarine is shrunken to microscopic size and injected into his blood stream with a small crew. Problems arise almost as soon as they enter the bloodstream.

Dr. Peter Duval: The medieval philosophers were right. Man is the center of the universe. We stand in the middle of infinity between outer and inner space, and there's no limit to either.
Col. Donald Reid: [General Carter goes to squash an ant that is crawling around among spilt sugar granules, then hesitates and finally relents as he reflects on how the crew in Benes' body are smaller than the ant] You'll wind up a Hindu; and love all forms of life, no matter how small.
[as the submarine enters the brain]
Dr. Duval: Yet all the suns that light the corridors of the universe shine dim before the blazing of a single thought...
Grant:
Dr. Michaels: Very poetic, gentlemen. Let me know when we pass the soul.
Dr. Duval: The soul? The finite mind cannot comprehend infinity - and the soul, which comes from God, is infinite.
Dr. Michaels: Yes, well, our time isn't.
Capt. Bill Owens: Mr Grant, send a message telling them that the Proteus is ready.
Grant: The Proteus, what's that?
Capt. Bill Owens: That's the name of this vessel; sounds better than calling it the U91O35.
Grant: [as the team enters a door marked "Sterilization Room"] How much can a man give to his country?
[Carter reaches out to kill a bug crawling on the table and changes his mind]
Col. Donald Reid: You'll wind up a Hindu. They respect all forms of life, however small.
Grant: What happened?
Capt. Bill Owens: Dr Michaels... went berserk.
Grant: Berserk nothing!
Dr. Michaels: Help! Get me out, my hands are trapped, I can't move my hands. I'm stuck and I can't... I can't move my hands... Get me out.
[white corpuscle begins to devour submarine]
Dr. Michaels: Get me out! Get me out!
General Carter: [after the briefing before the mission] Any questions?
Grant: Yes. When can I catch the next train back to town?
Cora Peterson: We're going to see things no one has ever seen before. Just think about it.
Grant: That's the trouble. I am.
Grant: Wait a minute! They can't shrink me.
General Carter: Our miniaturizer can shrink anything.
Grant: But I don't want to be miniaturized!
General Carter: It's just for an hour.
Grant: Not even for a minute!