On the subject of the correlation of neurological lesions with psycho-pathological phenomena, two eminent neuro-histologists, the Werthams, have recently written: “It must be pointed out that in proportion to the extraordinary complexity and differentiation of the finer functions mediated by the central nervous system, histological lesions are very gross. However we may conceive of the functional processes going on in the central nervous system—physiological, physico-chemical, metabolic, electrical, etc.—it should be obvious that only the grossest miscarriages and defects would become morphologically visible. Structural lesions are the effect of functional reactions that are not histologically demonstrable. Physico-chemical changes, metabolic processes, functional changes of blood-vessels, and similar biological phenomena that cannot be micro-histologically demonstrated, precede the anatomically visible lesions which occur only where the processes have attained a certain intensity. What we can demonstrate histologically in the nervous parenchyma is not by any means an adequate basis for the understanding of the quality, intensity or normality of nervous functions. In a patient who dies in the convulsions of tetanus, the anterior horn-cells may reveal nothing abnormal. Even the most minute and complete histological examination of the central nervous system in a case may fail to reveal any evidence of an existing profound disorder of brain function. There are cases of idiocy of the severest type in which no significant histological changes may be demonstrable in the brain.”