HEMOGENIC meningitis is the name proposed for the aseptic meningitis due to blood usually occurring one to five days after a subarachnoid hemorrhage, which may follow intracranial operations, craniocerebral injuries or ruptured or leaking intracranial aneurysms. The purpose of this paper is to present experimental evidence that specific breakdown products of blood are responsible for the aseptic meningeal reactions and hyperthermia observed when blood is present in the subarachnoid space. LITERATURE 1. Clinical Review. —The literature contains reports of aseptic meningeal irritation following spontaneous subarachnoid hemorrhage1and leaking or ruptured aneurysms.2 Mallory3reported a case of intracranial varicosities in which symptoms of meningeal irritation followed each episode of rupture. Such a clinical picture is not unlike that seen in patients with leaking aneurysms.2b The cerebrospinal fluid is usually pink to xanthochromic, but may be colorless.4 Aseptic meningeal reactions are often seen following craniocerebral injuries. Spurling