A characteristic change was the endarteritis,—of a focal nature with a few large mononuclear and lymphocytic cells pushing the intima inward at the edge of a lesion. In the more marked portion of the focal process, the thickness of the intima was greatly increased by proliferation. Great numbers of large mononuclear cells could be seen between the intima and the elastica. About these cells and interlacing among the other elements of the proliferating tissue was an excess of connective tissue fibres. The meningeal veins were more often diseased than the arteries; there was adventitial infiltration with lymphoid and plasma cells; sometimes the vein walls had become necrotic and infiltrated with polymorphonuclear leukocytes. It will be remembered that the left Sylvian artery was grossly thickened, and microscopic section of this vessel showed a partial thrombosis. The brain showed diffuse and focal changes. The _diffuse_ process was one of nerve cell degeneration and proliferative changes in the neuroglia and blood vessels, and no section of the many examined proved to be free from such changes, although in the majority of instances, these diffuse changes were slight. The cortical layers showed more of these diffuse changes than did the white substance. Barrett considered that the glial cell changes were more delicate indicators of the cortical changes than the nerve cell changes. He found rod cells, satellitosis, superficial gliosis, and a large gamut of changes in the neuroglia. There were two rather characteristic nerve cell changes: a shrinkage change going on to almost complete destruction, and a type of cell swelling, also apparently proceeding to complete destruction. [Illustration: 4. Arteritis of pia mater. ] [Illustration: 5. Focal vascular lesions. Case 57. Seven months from infection. “Disseminated syphilitic encephalitis,” Barrett. (Photographs by Barrett.) ] [Illustration: Paretic neurosyphilis (“general paresis”)—cerebral atrophy, _without_ meningitis. Therapeutics cannot hope to restore lost tissue. Duration. 3 years from beginning of well marked symptoms; 6 years from beginning of obvious symptoms; 12 years from a so-called “nervous prostration.” ] Among _focal_ changes, there were four main types: Areas of encephalitis, having the general appearance of granulation tissue, areas of simple necrosis or softening, apparently directly related to vascular changes near by, hemorrhages, and certain foci regarded as gummatous.