hygrology

from The Century Dictionary.

• noun That part of medical science which treats of the humors of the body.
• noun The study of the origin and properties of aqueous vapor, including its evaporation, condensation, pressure, relative humidity, density, weight, and all the relations of vapor or moisture to the atmosphere.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Med.) The science which treats of the fluids of the body.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun medicine The science that deals with the fluids of the body.