The Collaborative International Dictionary of English v.0.48:

Serolin \Ser"o*lin\, n. [Serum + L. oleum oil.] (Physiol. Chem.)
   (a) A peculiar fatty substance found in the blood, probably a
       mixture of fats, cholesterin, etc.
   (b) A body found in fecal matter and thought to be formed in
       the intestines from the cholesterin of the bile; --
       called also stercorin, and stercolin.
       [1913 Webster] Seron