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Gunnar F. Blix
JAMA. 1930;94(13):1011-1012. doi:10.1001/jama.1930.02710390109024.
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To the Editor:  —In The Journal, January 11, the refractive index of the spinal fluid was discussed in an editorial comment. The paper by Penfold and Price, whose work was mentioned, is not available to me. However, to judge from the data given it appears as if the questions of the normal variation, the significance and the utility of the refractive index of the spinal fluid are carried a bit further in the careful study by Bernhard Jacobowsky (Liquorstudien bei progressiver Paralyse mit besonderer Berücksichtigung der Veränderungen während der Impfmalaria, Upsala, Almqvist & Wiksells, 1929, pp. 14-48, 126-128). Unfortunately, this work has been published merely as a dissertation.On the whole, the refractive index of the spinal fluid seems a priori not to have much qualification as a diagnostic aid. Jacobowsky (p. 20) says: An increased refractive index proves that the composition of the spinal fluid is abnormal but does


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