Phylogenesis of the Nerve Cell

Abstract

There is not a single question in the biology which could be answered with so great difficulties as the one of phylogenesis. The first appearance, the past and formation of the living world in form and structure of to-day took place for millions and millions of years. The history and shape of the forming work of nature are completely far from the human experience and the possibilities of the real and objective analysis. One thing seems only to be sure for anybody who tries to understand the structure and function of the living matter and intends to follow the courses and ways of the changes which form new worlds and abolish them, that there is the everlasting law, according to which the living world of to-day developed from primitive forms innumerable years ago. These forms got due to permanent adaptation, more and more complicated structures and handed them down to their descendants. This part of the question offers no difficulties. It is verified by the comparative anatomy, the comparative physiology, the paleontology, the taxonomy, the serology, the biochemistry and even the molecular biology. But if we try to look for the descendance of the phyla, classes, orders, families and genuses of the animal kingdom, if we want to find the way, the procedure of the evolution of vertebrates from invertebrates, that of the birds and mammals from the reptiles and that of the man from the mammals, we ever encounter almost insurmountable difficulties.