The Collaborative International Dictionary of English v.0.48:

Phrenosin \Phre"no*sin\ (fr[=e]"n[-o]*s[i^]n or
   fr[e^]n"[-o]*s[i^]n), n. [See Phrenic.] (Physiol. Chem.)
   A cerebroside, related to cerebrin, present in white matter
   of the brain.

   Syn: cerebron.
        [1913 Webster + PJC]