Born in Germany, he gravitated to medicine and as a student in Munich he wrote on pathology of cortical cells in which he used a stain he created which opened up a new era in neurocytology and neuropathology. "Nissl Granules brought out by basic aniline stains perpetuate his name." But he also did outstanding work in psychiatry and demonstrated the correlation of nerves and mental disease by relating them to changes in glial cells, blood elements, blood vessels, and brain tissue in general. He worked with Alzheimer on general paresis. In the last 10 years of his life he did studies in which he established connections between the cortex and certain thalamic nuclei. He will be remembered as a great neuropathologist.