Meyer, Data of Modern Neurology. 137 



cation for the term 'segment'. In the cranial region the prin- 

 ciples for a plan of segmentation are more varied ; the origin 

 of the cranial nerves is more complex than that of the spinal 

 ones ; the segmentation of the skeleton is indistinct (we only 

 remind of the controversy on the vertebral theory of the skull 

 since Goethe's attemps of demonstrating a fusion of vertebrae 

 in the skull), and the complication of the neural tube is greater 

 than in the spinal segments owing to the complex sensory-mo- 

 tor mechanism of the head and owing to the centralization of 

 certain general mechanisms which help to form the * brain'. We 

 should however deprive ourselves of many useful analogies if we 

 should give up the segmental method in the cranial part of the 

 neural tube on account of these difficulties. From an architec- 

 tural point of view we do better to give up the term ' brain' 

 which means the entire intracranial nerve-mass and to dissolve 

 it into 'cranial segments and supcrseginental parts' . In this way 

 we obtain for the entire nervous system the following plan of 

 elements : 



1. Segmental neurones — the sensory and the motor 

 nerve-elements belonging to a segment (the 'peripheral nerve' 

 neurones and their 'nuclei' in the neural stem). 



2. The intersegmental neurones — nerve-elements which 

 merely connect various segments among one another ( forming 

 largely the ground-bundles and the formatio reticularis). 



3. The supersegmental neurones, constituting the cere- 

 bellar, midbrain and forebrain mechanism with their afferent 

 and efferent connections with the segments.^ 



'It is to be regretted that the term 'segment' has been used figuratively for 

 parts which cannot thus be cut out. Gowers, for instance, speaks of a cerebro- 

 spinal and a spino-muscular segment of the motor path. In order to avoid con- 

 fusion, we shall, in the following, reserve the term 'segment' for the purpose of 

 morphological divisions as described above. We do not, however, imply by this 

 an accurate segmentation in the sense of the metamerism of embryology, but 

 merely a functional topographical and 'practical' division. In principle the 

 division is alike ; but one of my segments may include several metameres. P, 

 Argutinsky has shown (Arch. f. mikr. Anat., Vol. 48, 1896) that a real gan- 

 glioform segmentation of the motor cells and of the cells of Clarke's column as 

 claimed by certain writers does not exist, but that certain intermediate cells 



