Cephalin is a phospholipid.
Although it is found in all living cells, it is found particulary in nervous tissue such as the white matter of brain and in spinal chord . Whereas Lecithin is the principal phospholipid in animals, cephalin is the principal one in bacteria. Its role in nature seems uncertain.
Chemically it is phosphatidyl-ethanolamine. Like Lecithin this consists of a combination of glycerol esterified with two fatty acids and phosphoric acid. Whereas the phosphate group is combined with choline in Lecithin, it is combined with the ethanolamine in Cephalin.
The two fatty acids may be the same, or different, and are usually in the 1,2 positions (though can be in the 1,3 positions).