Of recent years a considerable amount of study has been devoted to the nerve changes which are to be found in sane patients dying during the senile epoch, but comparatively little has been written concerning the alterations which occur in the nervous system of aged insane individuals. The object of this communication is to attempt from the pathologist's standpoint to elucidate some of these characteristic senile phenomena. I propose to briefly describe the morbid changes, both macroscopical and microscopical, which in my experience occur in aged insane persons, and to conclude by offering some remarks on the pathology of certain of these phenomena which I have particularly investigated. Before proceeding further, I would mention that the entire material for my observations has been afforded by the Lancashire County Asylum, Rainhill, and to Dr. Wiglesworth, the Medical Superintendent of that institution, I am indebted for permission to make use of that material and the asylum records in the compilation of this paper. My investigations have extended over a period of 18 months, and comprise the partial examination of the nervous system of all patients over 60 years of age who have died since my appointment as pathologist to the asylum. Of such cases θere have been 22 males and females their average age bone a matter of difficulty. In cases where no adhesion exists and the calvarium is readily removed, a slackness and dimpling of the dura mater—particularly of the frontal area—is generally seen, and proclaims an atrophy of the enclosed parts. The subdural hæmatoma or so-called pachymeningitis interna hæmorrhagica, so frequently met with in general paralysis of the insane, is not uncommon in senile insanity. Of 54 cases of that affection observed by Dr. Wiglesworth1 in this asylum, 12 occurred in patients over 60 years of age, while in a series of subdural hæmatomata collected by Sir J. Crichton-Browne and Dr. Bevan Lewis2 at the Wakefield Asylum, nine per cent, occurred in cases of “pure senile atrophy” of the brain, and 26·5 per cent. in cases of “chronic disorganization of the brain” (which, I take it, includes many senile cases); and, lastly, of the 50 cases of senility which I have examined, four presented this condition. The subdural fluid is invariably increased in quantity. The arachnoid membrane, particularly that covering the sulci and meningeal veins, is generally opaque, and the pacchionian bodies hypertrophied. A subarachnoid hæmorrhage I have only seen in one case, viz., in a demented female, æt. 78, who a few days before death suddenly became partially paralyzed in the extremities of the right side. At the autopsy an extremely wasted brain with a great excess of cerebro-spinal fluid was found, and lying in a hugely dilated subarachnoid space, situated at the point of junction of the horizontal limb of the intra-parietal sulcus with the post-central sulcus on the surface of the left hemisphere, was about 1½ ounces of dark, clotted blood and sanious serum. This was obviously pressing upon subjacent parts of the ascending parietal, superior parietal, and supramarginal convolutions—hence the paresis. The source of the hæmorrhage was not discovered, but that it issued from a ruptured, small pial vessel was doubtless. Further, that the hæmorrhage had actually occurred into the subarachnoid space was undeniable, as the stretched arachnoid membrane was clearly distinguishable confining it, and on the surface of the underlying cortex, which, by the way, was not lacerated, the delicate pia mater could be plainly traced. in fact, can often be detached in one sheet, but it does happen in some cases, especially if the brain be somewhat decomposed, that its removal is accompanied by a decortication exactly similar to that which is described as characteristic of general paralysis. In all the senile brains which I have examined there has been more or less atrophy and decrease in weight, and in some cases it has reached an extreme degree, leaving thin convolutions, and wide, shallow, gaping sulci. The frontal segment invariably suffers most, and the cerebellum and the mesencephalon participate in the wasting. The following table shows the average weight of the various parts of the brain in the cases I have examined:—