cot's theory. But if the figure be more closely examined, even here, all the larger vessels are seen to be infiltrated, and the process must be regarded as inflammatory. Its inflammatory nature becomes still less open to doubt if, in such a case, different parts of the central nervous system be examined. Indeed, inflammatory changes only in the vessels and in the interstitial tissue may occur. But the importance of the activity of the neurophages must not be overlooked. As I have said, their activity, especially in the most acute cases, undoubtedly plays an essential part in the degeneration of the ganglion cells; but pathologic examinations have already shown that even in individual cases this is by no means true for all parts of the central nervous system. Nor is it tenable in those cases in which extensive and well marked paralysis disappears completely in a very short time, for a neurophagocytic action of considerable degree is quite incompatible with speedy return of function.
There is reason to expect that experimental investigation will throw some light upon this question. Unfortunately, at present, we have extensive microscopic observations only of poliomyelitis in monkeys. Leiner and v. Wiesner have reported some cases of degenerative processes in the ganglion cells unaccompanied by inflammatory reaction. We must here admit that there is a strong direct action of the virus upon the ganglion cells. It is also certain, however, that no parenchymatous process can adequately explain the known changes in man. The descriptions of Landsteiner and Popper prove, moreover, that a purely parenchymatous affection rarely occurs even in monkeys. Leiner and v. Wiesner acknowledge that in a large number of cases infiltrations exist; they suppose that the parenchymatous and interstitial processes develop synchronously; and they maintain in their writings a position intermediate between the extremists of both parties. I may here remark that the apostles of the inflammatory nature of the malady do not attempt to deny the direct action upon the ganglion cells. As I belong to this category, allow me to quote from my latest work on the pathology of this disease. Emphasizing the fact that, in man, many factors undoubtedly point to the interstitial, as the more important changes, I call attention to the undeniable possibility of a direct influence upon the nerve tissue. It is possible that under certain conditions this influence may even
