American Retrospect

Epilepsy and other Convulsive Diseases: A Study in Neuro-dynamics and Pathogenesis.—Under this title Dr. Langdon, of Cincinnati, reviews (Journ. Nerv. and Mental Disease, September, 1896) the present state of our knowledge upon certain facts in the anatomy and physiology of the central nervous system; and puts forward some propositions to serve as a working hypothesis to explain epilepsy and other convulsive disorders in the light of modern histological research. He lays particular stress upon Cajal's demonstration of the individuality of the neuron as opposed to the older views. Though anatomically distinct units, neurons are in physiological relation with each other, by means of delicate projections termed gemmules or “contact granules.” The neuron-body (or nerve-cell) is to be considered, in his opinion, as mainly trophic in function; while the nervous activities themselves are to be looked for in the neuron processes, and accounted for upon the theory of inter-molecular and inter-atomic motion—this motion being the result of external stimuli acting upon the peripheral arborisations of neurons. In opposition to the many theories that have been advanced in the explanation and location of the epileptic convulsion, it is now almost universally conceded that: (1) the actual origin of the epileptic convulsion is in the cortex cerebri, and (2) that its nature is an “explosive discharge” in “unstable nerve tissue.” While the nerve-cell was considered the sole seat of all nervous activity, naturally the cause of convulsive phenomena was principally sought for within this nerve-cell. But Langdon quotes researches which show that the ultimate fibrillæ of the axis-cylinder may be traced through the neuron-body to finally ramify in “neuro-plexuses” composed of multitudinous interlacing “end-tufts,” with their contactbuds, and it is in this jungle that, in his opinion, any demonstrable lesions of the various convulsive disorders (including chorea, hysteria, and even uræmia) are to be sought. He is further of opinion that the cerebral cortex, instead of being a “centre of action,” has for its main function that of inhibition, in other words, that it is a centre for preventing, checking, directing and combining various activities which might otherwise occur in different order or intensity. The phenomena observed in the case of Goltz’ dog, which lived for eighteen months after having been deprived of its cerebral hemispheres, are cited in confirmation of this view. His propositions are summarised as follows:—(1) That epilepsy, the choreas, and probably most convulsive disorders, are the dynamical expression of an inhibitory insufficiency; not indications of an over production of nerve-energy, nor “explosions” due to a “molecular instability,” per se. (2) That the cause of this inhibitory insufficiency is to be sought for in the end-brushes of collateral processes of various cortical neurons, the situation varying with the type of the disease, whether sensory, psychic, or motor. (3) That the defect consists most probably in a structural incompleteness (small capacity, defective insulation, imperfect contact) or a numerical deficiency, or both, in the collateral processes of the neurons. (4) Defective collaterals may favour occurrence of convulsions in two ways: (a) by impairing connection with other neurons (inhibitory, storage?); (b) by increased “resistance” to overflow currents, causing temporary over-charging of motor axis-cylinders.