Ishmael is playing with words (besides saying that mood swings sometimes take control over him): "... whenever my hypos get such an upper hand of me ... " (notice that `hypos` are getting an `upper` hand; `hypo` = below, lower)
A few paragraphs later, Ishmael resumes and clarifies - in a mixture of self-deprecating and self-elevating glee - what he meant by `hypos getting such an upper hand`: "Now, when I say that I am in the habit of going to sea whenever I begin to grow hazy about the eyes, and begin to be over conscious of my lungs ... " (i.e. turning aimless, gloomy as well as turning into a person obsessing needlessly over own health).
Here's what authors of Wikipedia entry write about Moby-Dick's style: "The superabundant vocabulary of the work can be broken down into strategies used individually and in combination. First, the original modification of words as "Leviathanism"
[24] and the exaggerated repetition of modified words, as in the series "pitiable", "pity", "pitied" and "piteous" (Ch. 81, "The Pequod Meets the Virgin"),
[25] Second, the use of existing words in new ways, as when the whale "heaps" and "tasks."
[24] Third, words lifted from specialized fields, as "fossiliferous".
[24] Fourth, ..." (
Moby-Dick - Wikipedia, the free encyclopedia)
That same paragraph (it is one of the first paragraphs of the book) goes on, showing off what's ahead for the reader in terms of "superabundant vocabulary"; reading the whole thing:
*
"Now, when I say that I am in the habit of going to sea whenever I begin to grow hazy about the eyes, and begin to be over conscious of my lungs, I do not mean to have it inferred that I ever go to sea as a passenger. For to go as a passenger you must needs have a purse, and a purse is but a rag unless you have something in it. Besides, passengers get sea-sick- grow quarrelsome- don't sleep of nights- do not enjoy themselves much, as a general thing;- no, I never go as a passenger; nor, though I am something of a salt, do I ever go to sea as a Commodore, or a Captain, or a Cook. I abandon the glory and distinction of such offices to those who like them. ... "
Since up to 4 sentences of quoting are permitted here, and since Moby-Dick is in public domain, please visit:
Moby-Dick; or, The Whale - Chapter 1 - Loomings for the remaining ~750 pages.
EDIT: I've quite enlarged the original 2-sentence post (for the sake of the great book, not 19th century shifting usage of `hypo`, although, that's how it started, of course).
* Edited at request of poster to reduce quotation. Cagey, moderator.