inogen

from The Century Dictionary.

• noun A hypothetical complex substance which is assumed by certain physiologists to decompose in the muscular tissue during contraction, yielding carbonic acid and lactic acid and a nitrogenous body, and to be re-formed during repose.

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

• noun (Physiol.) A complex nitrogenous substance, which, by Hermann's hypothesis, is continually decomposed and reproduced in the muscles, during their life.

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

• noun organic chemistry, obsolete A complex nitrogenous substance formerly hypothesized to be continually decomposed and reproduced in the muscles during life.