The group of Iipins1 contains two main subdivisions; (a) The phoSph9lipins -(phosphaddes) comprising an unknown number of substances, grouped in three classes, the lecithins, the kephalins, and the sphingomyelins. It is now recognised that the ' . lecithin, kephalin, and sphingomyelin prepared from plant and animal sources are not single substances but mixtures of individuals, conforming to the same type of structure but differing in the nature of the two fatty acid groups in the molecule.

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... er class of phos pholipins of complicated structure have been isolated from the tu bercle bacillus, but at present the constitution of these is unknown. (b) The galactolipins (cerebrosides) comprising phrenosin (cere brone), kerasin, nervone, and hydroxynervone. These are regarded a� well-characterised substances of the same type of structure, dif f�ring only in the nature of the single fatty acid radical present. Ifis possible that small amounts of other yet unidentified galactolipins may be present in these as impurities. THE PHOSPHOL.IPINS