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152 Remak as existing upon these fibres. The similarity between the organic fibres and that which I have described as the earlier condition of the white nervous fibres, might be adduced as an objection to my description of the formation of nerves, and it might be said, that that form seemed to be the earlier form of the white nervous fibre, because the organic nerves were developed earlier than the white, and, therefore, organic fibres were the only ones present in the first instance. Observation of the actual transition, as represented in pl. IV, fig. 8, c d, would, however, refute this argument. Each pale, nucleated fibre becomes a white nervous fibre, as an immediate consequence of the formation of the white substance, which is probably a secondary deposit upon the internal surface of the hollow fibre. The formation of this white substance, which, according to analogy, must occur in every one of the minutest fibres, either does not take place at all in the organic fibres, or does so at a much later period, and their peculiarity therefore consists in their remaining stationary at an earlier stage of development, and either never attaining to the higher development of ordinary nerves, or only at a much later period, (a point which might be decided by comparing their numbers in old and young individuals.) One can conceive that the function of the organic nerves, whether it be actually a chemico-vital one, or consist merely in the production of involuntary motion, requires less-developed nerves, in the same way that the involuntary muscles do not attain the same degree of development as the voluntary.

These occur in the gray substance of the brain and spinal cord and in the ganglia, having generally the appearance of comparatively large granulous globules, enclosing a round vesicle, placed eccentrically, and which again exhibits in its interior one or two small dark points. According to Remak, two of these vesicles sometimes occur in one globule. Valentin (Nov. act. Acad. Leopold. xviii, p. 196), calls attention to the similarity between their composition and that of the egg, he compares the vesicle of the ganglion-globules to the germinal vesicle, their parenchyma to the yelk-substance, and ascribes