134 Journal of Comparative Neurology. 



get an orientation of the heavy Hnes of architecture of the ap- 

 paratus under study, making use of the solid data, but not 

 expressing any opinion yet on the details of interrelation 

 between the 'neurones.' We assume as a working hypothesis 

 that the * neurones ' are units such as His and Forel and also 

 Cajal describe them, but avoid any assumptions which would 

 necessarily collide with any of the difficulties just reviewed. 



Outline of an Architecture of the Nervous System. 



In order not to move in abstract realms, we give in the 

 following pages a short outline of the general architecture of 

 the nervous system. We shall then be able to refer to con- 

 crete conditions in such a manner as to avoid misunderstanding. 

 We must necessarily take some position in the general method 

 from which to approach neurology, and we choose the one of 

 evolution in this sense that we take the phylogenetically oldest 

 mechanisms as the starting point instead of proceeding from the 

 cortex through the ' projection-systems ' after Meynert's 

 fashion. 



We are inclined to start in a consideration of the nervous 

 system from an assumed unit, the brain, and to look upon the 

 peripheral nerves as its afferent and efferent wires. This meth- 

 od has great disadvantages. It starts out with what is least 

 known and most complicated and creates an ego-centric view of 

 the human mechanism which stands in the way of an under- 

 standing of many of the most useful facts acquired by neurolo- 

 gy. In building up the following sketch, we begin at the foun- 

 dation, and proceed towards the most differentiated mechanisms 

 after having established the ground upon which to build them. 



We start from a sketch of the nervous system of a worm. 

 The rain-worm is a distinctly segmented animal, bilaterally 

 symmetrical, as the vertebrates. Its nervous system consists 

 of a head-ganglion above the oral opening, a strand on each side 

 of the oesophagus extending from it to the first ganglion of the 

 ventral ganglion-chains and forming what the Germans call the 

 ' Schlundring ', and the ventral ganglion-chain formed of a ven- 



