The Collaborative International Dictionary of English v.0.48:

kephalin \keph"a*lin\ (k[e^]f"[.a]*l[i^]n), n. [Gr. kefalh` the
   head; it was supposed by Thudichum to exist in brain tissue.]
   (Physiol. Chem.)
   One of a group of phospholipids (nitrogenous phosphorized
   fatty substances), present in all living cells and
   particularly noticeable in nervous tissue. Same as
   cephalin, which see.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

cephalin \ceph"a*lin\ (k[e^]f"[.a]*l[i^]n), n. [Gr. kefalh` the
   head; it was supposed by Thudichum to exist in brain tissue.]
   (Physiol. Chem.)
   One of a group of phospholipids (nitrogenous phosphorized
   fatty substances), present in all living cells and
   particularly evident in nervous tissue. The cephalins consist
   of glycerol phosphate in which the two free hydroxyls of the
   glycerol are esterified with fatty acids, and the phosphate
   forms an ester linkage to the hydroxyl of ethanolamine. The
   phosphate may be linked to the alpha (end) or beta (middle)
   hydroxyl of the glycerol portion. The natural isomers are of
   the alpha form, and have the general formula
   R.O.CH2.CHOR'.CH2.O.PO2.O.CH2.CH2.NH2, where R and R' are
   the acyl residues of long-chain fatty acids, which may be the
   same or different. [Also spelled kephalin.]

   Syn: phosphatidylethanolamine. [PJC]