![]() ![]() ![]() The top portion of this layer, or apical cap, becomes the brain. The outer layer of the initial sphere will become the nervous system, in analogy with the ectoderm. These deformations, combined with the variables of segmentation, thickness, and elasticity, determine the phyletic form created as the membrane curls inside its original sphere and grows as an embryo. As the membrane involutes (turning inside out) at the blastopore, folds, ripples, and grooves are formed. The thickness and elasticity of the lipid membranes are parametric variables in the mechanically driven process that determines the possible paths toward the eventual form. It is the mechanical events of gridding and gastrulation that determine the resultant forms of the embryo and eventual adult. The lipid membrane blastula, a hypothetical multilayered gridded sphere, goes through the process of gastrulation, becoming the embryo. Additionally, it accounts for the sequence through which the multilayered egg undergoes gastrulation and becomes the now inside out multilayered body with the nervous system as the innermost layer. It also accounts for the spatial interaction between the formation of the brain, spinal cord, and nerves with the corresponding formation of vertebrae and skull. This model accounts for the formation of the lobes of the brain, the spinal cord, and the spinal nerves. In this way the regions of the brain are mapped by the creation of “fate maps” identifying the regions of the egg that originate the regions of the brain. Here, the architecture of the mature brain is traced back to its pregastrulation state, a hypothetical gridded sphere. The physical, topological, and fluid mechanisms of the blastula surface during gastrulation produce the eventual forms of the organism. The mechanical algorithm reported here is the continuation, if not completion, of the Entwicklungsmechanik movement. Notably, Wilhelm His (called “the father of human embryology”) made experiments with the mechanical deformation of rubber bladders and tubes that mimic the shapes of the brain (His 1874). A serious attempt to account for its shape was made by the Entwicklungsmechanik, or developmental mechanics movement of the late nineteenth century. The history of the study of the structure of the brain began with the sixteenth century anatomists from Leonardo da Vinci and Vesalius to Eustachius and Fallopius who successfully described the organ in detail. The first step of embryogenesis is gastrulation, where blastula is pressed to enter its own interior, pulling the surface inside out, forming the embryo. The hypothetical model is in close analogy with nature: the blastula is a segmented gridded sphere which results from the subdivision of the egg. This paper proposes a hypothetical construction based on the discovery of a simple algorithm which generates topologically the form of the brain, the spinal cord, and the vertebral column by the deformation of a gridded segmented sphere by the inversion of its surface. Neurology does not teach how the brain gained its shape, nor have any causative theories of brain formation been published in recent times. But morphogenesis, the origin and cause of these forms, has not been studied since the last half of the nineteenth century. The morphology of these organs and the observed steps of neural development are well described, consequent of centuries of study. This paper reports the discovery of a geometrical algorithm that provides a coherent step by step mechanical account of the structure of the nervous system, including the vertebrate brain, the spinal cord, the vertebral column, and the spinal nerves.
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