This excitement lasts for a short time only, but often recurs. In nine per cent of the cases (Kleist) death results from heart failure, septic infection or other intercurrent diseases. Wassermann and Westphal demonstrated streptococci in the brain in several cases of chorea. Others have reported staphylococci in the blood. Choreic delirium is usually associated with endocarditis or rheumatic infections, and occurs in the acute type but not in the Huntington variety of the disease. Delirious excitements, according to Kraepelin, also occur in acute cerebrospinal inflammatory processes and may be due to furunculosis or caused by infections from the mouth or the intestinal _tract_. There is nothing particularly characteristic in such conditions aside from their severity. They have been collectively described under the designation of "acute delirium." Their differentiation depends entirely on the demonstration of the source of infection. The anatomical basis for these disturbances is always found in the cerebral cortex. The pia is infiltrated with lymphocytes and plasma cells and leucocytes are found in the perivascular spaces. There is also a proliferation of the glia. The "grave" alteration of Nissl is often demonstrable. After the infectious process passes its maximum intensity and the delirium disappears, "residual" delusions may remain with a clear sensorium. These may last for several days or even weeks. They frequently follow typhoid fever. Occasionally hallucinations of sight and hearing persist in the same way.