Spinal ganglionic cells of Rana pipiens were studied with light and electron microscopes in normal animals and in animals which had received graded dosages of malononitrile intraperitoneally. After treatment no increase in the intensity of staining was noted in the Nissl substance when spinal ganglion cells were examined with the light microscope. The electron micrographs demonstrated the following in malononitrile-treated animals:
1. The cisternae of the endoplasmic reticulum composing the Nissl bodies appeared to fragment and lose their parallel orientation.
2. The microvesicular components of the Golgi complex appeared to increase in number, and the increase was apparently due to fragmentation of the membrane system of the Golgi complex.
3. The mitochondria enlarged and became pleomorphic, but displayed no alterations of internal structure.
The morphological changes may be interpreted as reflections of biochemical alterations.