The "Quaking" mouse is a recessive autosomal mutant characterized by a deficient myelination of the central nervous system.The disease is recognized at about the twelfth day after birth and reaches its full expression by about three weeks. The animal has an unsteady gait and a marked tremor of the hind quarters; epileptic fits are induced by sensory stimulations a t the adult age. This mutation apparently involves the process of myelin formation; there is no evidence of destruction. The analysis of brain fatty acids and lipids was undertaken to find out if the inyelin deficiency involves an inborn error in the metabolism of one of its major constituents. "Quaking" males aged from seven to ten weeks were compared to apparently normal litter-mates. At this stage, myelination is achieved. Brain lipids are diminished, especially galactolipids. Qualitative modifications of cerebrosides, sphingomyelin and sulphatides have been detected by mono and two dimensional thin layer chromatography. The proportion of long chain fatty acids (especially CZ4) is greatly diminished, as shown by gas chromatography. This is true for both cerebrosides and sphingomyelin.I n conclusion, the long chain fatty acids of galactolipids and sphingomyelin are considerably diminished in the "Quaking" mouse. Whether it is a cause or a consequence of myelination deficiency remains to be proved, although the importance of the alteration is in favour of the first hypothesis.Sidman et al. [I] were the first to describe the recessive and autosomal "Quaking" mutation observed in 1961 at the Jackson Laboratory[2] in strain DBA of the black mouse. It is characterized by an impairment in myelin formation of the central nervous system.The disease is recognized at about the twelfth day after birth and reaches its full expression by about three weeks. The animal has an unsteady gait and a marked tremor of the hind quarters; epileptic fits are induced by sensory stimulations at the adult age.The entire central nervous system is considerably deficient in myelin [l]; however, some fragments of myelin are present in almost all tracts. There is no evidence of destruction, no globoid cells, no metachromatic lipids and no inflammation ; the neurons, the axons, the glial cells appear normal, as well as myelin of the peripheral nervous system.Non-Standard Abbreviations. Fatty acids are identified by the carbon number and number of double bonds (18:O = stearic acid); h indicates the presence of a 2-hydroxy group.

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