EDITORIAL. 



TWO RECENT TENDENCIES IN CEREBRAL MORPHOLOGY. 



Many diverse lines of current biological research are putting 

 emphasis on the functional unity of the living animal body. Nor- 

 mal growth, regulation, coordination of reactions and the mani- 

 fold phases of adptation all point the same way. The degree of 

 perfection of the integrative function of the nervous system in 

 higher vertebrates is determined not only by the complexity of the 

 central internuncial or associational conduction paths, but quite 

 as much by the extent and character of the differentiation of the 

 receptors and effectors, i.e., the nature of the correspondence (in 

 the Spencerian sense) between the organism and the environment. 

 The central nervous system cannot therefore be studied com- 

 paratively to the best advantage by itself, but only in relation 

 with the peripheral nervous system and indeed with the body as 

 a whole. 



Recent students of the phylogeny of the vertebrate nervous 

 system, recognizing this principle, have adapted themselves to it 

 in two very different ways. The anatomists of one group have 

 made an especial study of the mechanical factors in cerebral archi- 

 tecture, such as the effects on the brain of ontogenetic or phylo- 

 genetic changes in the form of the cranium, position of peripheral 

 organs, vascular supply, arrangements of the non-nervous parts 

 of the brain, etc. The anatomists of the other school have placed 

 more stress upon the conduction paths and have devoted them- 

 selves to the exposition of the architectural effects of variations in 

 the physiological importance of the several functional systems of 

 neurones of which the nervous system is composed. Differences 

 in the functional patterns or action systems of animals involve 

 parallel differences in the architecture of the nervous system 

 and the solution of many problems is sought in a comparative 

 study of functional systems of neurones, correlating the variations 

 in anatomical structure with differences in physiological value or 

 behavior. 



