132. The histological question is raised into undue importance because it is supposed to carry with it physiological consequences which would deprive the neuroglia of active co-operation in neural processes, reducing it to the insignificant position of a mechanical support. I cannot but regard this as due to the mistaken tendency of analytical interpretation, which somewhat arbitrarily fastens on one element in a complex of elements, and assigns that one as the sole agent. Whether we call the neuroglia connective or neural, it plays an essential part in all neural processes, probably a more important part than even the nerve-cells, which usurp exclusive attention! To overlook it, or to assign it a merely _mechanical_ office, seems to me as unphysiological as to overlook blood-serum, and recognize the corpuscles as the only nutrient elements. The notion of the neuroglia being a mere vehicle of support for the blood-vessels arises from not distinguishing between the alimental and instrumental offices. In the function of a limb, bone is a co-operant. In the function of a centre, connective tissue is a co-operant; so that even if we acknowledge neuroglia to be a special form of connective tissue, it is an agent in neural processes; _what_ its agency is, will be hereafter considered. Following Bidder and Kupffer, the Dorpat school proclaimed the whole of the gray substance of the posterior half of the spinal cord to be connective tissue; and Blessig maintained that the whole of the retina, except the optic fibres, was connective tissue.[161] Even those anatomists who regarded this as exaggerated, admitted that connective tissue largely enters into the gray substance, especially if the granular ground substance be reckoned as connective, the nerve-cells being very sparse in the posterior region. Be it so. Let us admit that the gray matter of the frog’s spinal cord is mainly composed of neuroglia, in which a very few multipolar nerve-cells are embedded. What must our conclusion be? Why, that since this spinal cord is proved to be a centre of energetic and manifold reflex actions--even to the extent of forcing many investigators to attribute sensation and volition to it--this is proof that connective tissue does the work of nerve-tissue, and that the neuroglia is more important than nerve-cells! Three hypotheses are maintainable--1°. The neuroglia is the amorphous ground-substance of undeveloped tissue (neuroplasm) out of which the cells and fibres of nerve-tissue and connective tissue are evolved. 2°. It is the product of dissolved nerve cells and fibres. 3°. It is the undeveloped stage of connective tissue. For physiological purposes we may adopt any one of these views, provided we keep firm hold of the fact that the neuroglia is an essential element, and in the centres a dominant element. To make this clear, however, we must inquire more closely into the relations of the three elements, nerve-cells, fibres, and neuroglia.