The vaso-motor hypothesis is held by Rosenthal,[25] who, however, wrongly {212} gives the spinal cord the preponderating part in the production of the symptoms. According to this author, the anæsthesia and analgesia present in hysteria conform to the law as established by Voigt with regard to the distribution of the cutaneous nerves. The sensory nerves form at the periphery a sort of mosaic corresponding to an analogous arrangement in the spinal cord. “It is evident,” he says, “that the peripheral disorders in hysteria merely represent an exact reproduction of the central changes, and that the latter are situated, in great part, in the spinal cord.” He attributes a large part of the symptoms of hysteria to a congenital or acquired want of resistance of the vaso-motor nervous system. “Motor hysterical disorders are also due in the beginning to a simple functional hyperæmia, but in certain forms the chronic hyperæmia may lead to an inflammatory process which may terminate (as in Charcot's case) in secondary changes in the columns of the cord and nerve-roots.” When the brain is involved in hysteria, he holds that the most serious symptoms must be attributed to reflex spasms of the cerebral arteries and to the consequent cerebral anæmia. [Footnote 25: “A Clinical Treatise on Diseases of the Nervous System,” by M. Rosenthal, Vienna, translated by L. Putzel, M.D., vol. ii. _Wood's Library_, New York, 1879.] The dynamic pathology of hysteria is probably believed in by most physicians, and yet it is difficult to explain. Thus, Briquet[26] says that hysteria manifests itself by derangement of the nervous action, and what is called nervous influence is something like electricity. It is simply the result of undulations analogous to those which produce heat and light; in other words, it is a mode of movement. Wilks[27] compares some of the conditions found in hysteria to a watch not going; it may be thought to be seriously damaged in its internal machinery, yet on looking into it there is found a perfect instrument that only needs winding up. As regards the brain being for a time functionless, the possibility of this is admitted by all, as in sleep or after concussion. He mentions the case of a young girl who had been assaulted, and had complete paralysis of motion and sensation. The shock had suspended for a time the operations of her brain, and organic life only remained. We have only to suppose that half of the brain is in this way affected to account for all the phenomena of hemianæsthesia. [Footnote 26: _Op. cit._] [Footnote 27: _Lectures on Diseases of the Nervous System_, delivered at Guy's Hospital, by Samuel Wilks, M.D., F. R. S., Philada., 1883.] According to the dynamic view, the central nervous system is at fault in some way which cannot be demonstrated to the eye or by any of our present instruments of research. The changes are supposed to be molecular or protoplasmic, rather than vaso-motor or vascular.