We shall describe separately the lesions of the encephalon, spinal cord, peripheral nerves, and viscera.

Pathological Anatomy. A. Encephalon

Dura mater: often congested, presenting occasionally the lesions of hemorrhagic pachymeningitis.

Pia-arachnoid and brain.

(a) Macroscopic lesions.

(1) General atrophy of the brain, most marked in the frontal and parietal lobes, and made evident by:

α. Flattening of the convolutions;

β. Thinning of the cortex;

γ. Diminution of the weight, most marked in cases of slow evolution, often slight or absent in cases of general paralysis of very rapid course.

(2) Thickening of the pia mater and adhesions between it and the cerebral substance: stripping off the pia causes a tearing away of the cerebral substance, especially at the frontal and parietal lobes.

(3) Arteritis of the large and medium-sized cerebral vessels: this lesion is not a constant one.

(4) Ependymal granulations: the lining of the ventricles is thickly studded with translucent granulations, which are sometimes very minute, like a fine powder sprinkled over the surface, but more often coarser, resembling grains of granulated sugar. Ependymal granulations are fairly constant in general paralysis; outside of general paralysis they are found only exceptionally.

(6) Microscopic lesions.1

(1) Nerve Cells

Their changes are: a. In numbers and arrangement: many cells disappear; the different layers are more difficult to distinguish than in the normal state and appear to be confounded;

1 Ballet. Les lesions cerebrates de la paralysie generate. Ann. med. psych., 1898. - Anglade. Sur les alterations des cellules nerveuses dans la paralysie generate. Ann. med. psych., July-Aug., 1898. - Alzheimer. Histologische Studien zur Differenlialdiagnose der progress. Paralyse. Histol. u. histopathol. Arbeiten. Vol. I, 1904.

β. In shape: the processes disappear, the angles become blunted, the cell-body tends to reduce itself to a small, granular and pigmented mass;

γ. In structure: chromatolysis - that is, alteration and destruction of Nissl's corpuscles - which causes the cell to assume a hyaline aspect when the chromatic substance is destroyed, or to present a uniform coloration if stained by the aniline pigments when this substance, reduced to a fine powder, is disseminated through the entire cell.

(2) Nerve-fibers: many are destroyed, which fact can be demonstrated by Pal's or Weigert's hematoxylin stain. The degeneration affects projection fibers as well as association fibers, but more particularly the superficial tangential fibers of Exner-Tuczek.

(3) Pia mater and blood vessels: a. The pia mater is thickened, infiltrated by nuclei representing proliferating fixed connective-tissue cells or migrating leucocytes.

/3. The blood vessels are much more numerous than normally; the walls are thickened, often showing hyaline or fatty degeneration; the perivascular spaces are infiltrated with cells. The appearance of these lesions is similar to those of diffuse cerebral syphilis.1

Among the cells infiltrating the pia-arachnoid and the adventitial coats of the cortical vessels a special variety of cells occurs, known as plasma cells, which are of great importance in pathological diagnosis, since they are constant in general paralysis and are found, according to Nissl, in no other chronic psychosis. These cells are somewhat larger than the ordinary round cells, contain coarse, deeply stained granulations in their nuclei, and a relatively large amount of finely granular protoplasm which, in specimens fixed in alcohol and stained with toluidin blue, takes a deep purple stain.

1 Mahaim. De l'importance des lesions vasculaires, etc. Bullet, de l'Acad. roy. de Med. de Belgique, July, 1901.

(4) Neuroglia

Proliferation of neuroglia-cells is very frequently seen; when well marked it is especially prominent in the vicinity of the blood-vessels (Mahaim). Scantily distributed here and there may be seen spider-cells of abnormal shape and of gigantic size.

Among the most constant neuroglial changes must be mentioned the ependymal granulations already referred to above. These are found under the microscope to consist of irregular hillocks upon the lining of the ventricles, formed by great proliferation of the ependymal glia cells which, instead of consisting of a single layer, as they do normally, are in these hillocks piled up in half a dozen or more irregular layers.

(B) Spinal Cord

(1) Nerve cells: degenerative and atrophic lesions identical with those of the cerebral cells.

(2) Nerve-Fibers

There are two principal types of lesions - the tabetic type and the type of combined sclerosis.

(A) Tabetic Type

The degeneration is localized in the posterior columns and is similar to the lesion of tabes: this has led many authors to look upon general paralysis and tabes as two different localizations of the same morbid process.1

(6) Combined Sclerosis

The degeneration involves both the posterior and the lateral columns. Moreover, the process here is more diffuse and affects simultaneously different systems of fibers (tract of Gowers, crossed pyramidal tract).

(C) Peripheral Nerves

The lesions of the peripheral nerves consist in the phenomena of neuritis and atrophy, analogous to those encountered in tabes and in alcoholism.

(D) Viscera

Three classes of lesions may be distinguished in the viscera:

(1) Lesions occurring merely as accidental complications: various infections, broncho-pneumonia, tuberculosis. The latter is rare and usually runs a slow course.

1 Nageotte. Tabes et Paralysie generate. These de Paris, 1893.

(2) Lesions which are the direct consequences of the nervous disorders. These have been studied exhaustively by Klippel, who has termed them vasoparalytic lesions. They consist, according to this author, "in a high degree of congestion and capillary engorgement, capillary hemorrhages, and, by consequence, atrophic degeneration of epithelial tissues." l

(3) Diffuse vascular lesions identical in appearance with those of the cerebral vessels.

These lesions are met with chiefly in the kidneys, liver and heart, and are often associated with degenerative lesions, such as fatty or cirrhotic liver, sclerotic kidney, or degenerated myocardium.