The following text is from Bram Stoker's 1897 novel Dracula. The narrator is being driven in a carriage through a remote region at night.

The baying of the wolves sounded nearer and nearer, as though they were closing round on us from every side. I grew dreadfully afraid, and the horses shared my fear. The driver, however, was not in the least disturbed; he kept turning his head to left and right, but I could not see anything through the darkness.

As used in the text, what does the word "disturbed" most nearly mean?