1. A method for the histochemical demonstration of the lipid of the cytoplasmic network (‘Golgi apparatus’, ‘Nissl complex’) of the neurones of vertebrates was accidentally discovered.
2. Very small pieces of tissue are fixed in Lewitsky/calcium or Flemming/calcium, postchromed, and embedded in gelatine. Frozen sections are cut at 0.5 to 5 µ, and coloured in Sudan black after bleaching.
3. The intensity of the colouring of lipid by Sudan black can be increased by centrifuging the tissue before fixation.
4. The method described in this paper demonstrates lipid in the strands and bodies of the cytoplasmic network of vertebrate neurones. It was shown, in sections subsequently decolorized and then stained in a basic dye, that the sudanophil reticular objects are the Nissl complex.