Macroneurotrophism in the Development of the Vertebrate Skeleton - Roth - 1994

Further argumentation and experimentation is presented to buttress the author's endeavours to extend the cerebrocranial developmental "macroneurotrophic" interrelation , viz., the formative effect of the growing brain upon its bony encasement to the entire developing bony and nervous tissues of the vertebrate body. Even the extracranial skeleton develops in the most intimate interrelation with the actively growing spinal and peripheral nervous structures. Against the petrified belief that the growth of the extracerebral nervous structures is mere passive "innervation follower" of the other tissues to be innervated, the view is defended and experimentally supported that growth in length of the bony skeleton depends upon and is governed by the active co-growth of the nervous skeleton (tenn by Donaldson 1937). Variable length of the vertebral column as well as of the limb bones in animals and man mirrors the variable growth-in-length potentiality of the spinal and peripheral nervous structures. The nervous skeleton perceives, along exteroceptive and proprioceptive path ways, the conditions prevailing in the environmental niche and provides, by mediation of the more or less extensive neural growth, for the appropriate shape and length of the bony skeleton. Impairment of the vulnerable neural growth results in "neuroadaptive" deformities of the skeleton consisting in various types of its shortening, i.e. accumulation of the proliferating skeletogenic material along and within the too short nervous skeleton. In a number of instances experimental "osteoneural" findings pattern what happened in the course of evolution and hominization, viz., primary shortening of the nervous skeleton reflected in corresponding transfonnations of the bony skeleton. Shortening of the human mandible with appearance of the chin is one of the most striking examples of such an (experimentally reproducible) "phylogenetic neuroadaptive deformity". It is argued that egg and sperm appear to be sources of the two basic growth types of the vertebrateb ody, the cellular-divisional and the neural-extensive. The possible repercussions of that developmental interrelation upon some problems of general biology are discussed.

Keywords

Bony skeleton - Nervous skeleton - Macroneurotrophism - Neuroadaptive skeletal dysplasias - Neuroadaptive evolution of the skeleton

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