From the data provided by our investigations we may conclude that in all pathologic processes of the cortex which end in dementia and death, the fatty degeneration of the elements of the cortex plays a not unimportant part. The characteristic change for most of the psychoses is found in a great increase in amount of fatty deposits when compared to normal individuals of the same age. In some processes such as senile dementia and dementia præcox the fatty substance appears to fill completely the cell body, and these cells have apparently lost all their functioning power. It is not common to find the fatty deposits in the processes of the ganglion cells except in dementia præcox, and to a limited extent in senile dementia.
In other cases the pathological variety of the fatty deposits in the ganglion cells is seen to be diffused over the whole ganglion cell. We were able especially to observe this in infectious psychoses, in general paralysis, and in epilepsy. The so called central neuritis assumes a peculiar attitude in that it plainly leads swiftly to an acute fatty degeneration of the ganglion cells, in which there exists an inclination of the fatty granules to flow together into large masses. Frequently the fatty degeneration of the ganglion cells appears to be connected with the sclerosis of the cells, especially when it is a matter of slowly progressing alterations of degeneration. The behavior of the glia is not wholly uniform in the various disease processes. In chronic disease processes we often find that the extent of the fatty accumulations in the ganglion cells does not correspond to an equal increase in the glia cells, while the otherwise acutely degenerative alteration in the nuclei of the glia is noticeable. In acute processes we see regularly an equal accumulation of the fat in both species of cell. The conditions of the cells in the vascular wall are wholly similar to those of the glia cells. We must therefore assume that in chronic diseases the fatty substance has been carried out of the glia and the vascular walls while it has been retained longer in the ganglion cells. Among all the disease processes amaurotic idiocy assumes a peculiar position. We have observed that in addition to the fatty materials of the scarlet fat stain, still other fatty materials, lipoid in character, have made their appearance. While the study of the fatty deposit in the cerebral cortex offers some points for a differential diagnosis, yet it is not adopted in all cases, since the distinction in individual disease processes is not always characteristic. From the preceding examination, however, in many cases there result important findings which briefly we summarize as follows:
1. In all degenerative alterations in the cerebral cortex the mass of the lipoid materials in the ganglion cells in comparison with that in healthy individuals of equal age is found to be considerably augmented. In the alteration of the lipoid materials in the ganglion cells two types in general may be distinguished: (a) An augmentation of the lipoid materials in the ganglion cells, in places where normally a small amount of fat is found, (b) An augmentation of the lipoid materials over the entire cell.
2. The first type we find also characteristic in senile dementia. The second type occurs in acute infectious psychoses, general paralysis, and well advanced epilepsy.
3. While the advanced lipoid degeneration of the ganglion cells in senile dementia has already been described in many ways, it has appeared from our investigations that also in the young chronic cases of dementia præcox far-reaching fatty degeneration of the ganglion cells, especially in the second and third cortical strata, likewise occurs. These findings should constitute an important contribution to the pathological anatomy of dementia præcox.
4. The so called central neuritis represents a peculiar disease process according to the appearance of the fatty degeneration, since this fatty degeneration reaches a very advanced degree, and also in so far as it deviates from other disease processes in that here there comes out very distinctly in the picture an inclination of the fatty granules to flow together.
5. Amaurotic idiocy also represents a particular disease process in respect to the lipoid degeneration, since here in addition to otherwise distributed scarlet stain lipoid materials, still other specific lipoid materials make their appearance.