Meyer, Data of Modem Neurology. 14I 



we have seen, there is a primary morphological division into 

 three 'vesicles' (the division into five vesicles had better be 

 abandoned, since it is partly artificial and because it cannot be 

 carried out with advantage). We recognize the rhombenceph- 

 alon or hind brain, the midbrain and the forebrain (thalamus 

 and hemispheres). From a physiological and architectural 

 point of view, we recognize in this ' brain ' elements of segmen- 

 tal connections, and further the special supersegmental mechan- 

 isms, the cerebellar, midbrain, and forebrain apparatus. 



In the human brain, we can conveniently outline the fol- 

 lowing cranial segments : 



1. Those of the mechanisms of respiration, of articula- 

 tion and of deglutition. The hypoglossal nerve supplies the 

 muscles of the tongue ; the pneumogastric, the viscera of the 

 neck, thorax and abdomen, and the glossopharyngeal makes the 

 connections for the reactions to stimulation of taste. These 

 mechanisms are located in the body segments belonging to the 

 lower part of the medulla oblongata or hind-brain. 



2. The auditory- facial-abducens segment. Here we find 

 on the ' sensory ' side the auditory nerve in connection with 

 the cochlea of the inner ear, and the equilibration (?) nerve, in 

 connection with the semicircular canals, the sense organ for cer- 

 tain auditory qualities and 'appreciation of position in the space.' 

 We know that destruction of the two produces deafness and 

 dizziness and inability of equilibration. The motor side of this 

 segment is represented by the facial nerve which moves the skin 

 and muscles of the face, and, especially in animals, the exter- 

 nal ear ; and the abducens nerve, which moves the eyeball out- 

 ward. It is easy to remember the function of this segment in 

 in this way ; you hold a watch near the ear of a dog and he 

 will prick up his ear and turn the eye to the side ; the addition- 

 al movement of the head depends on an association mechanism 

 with other segments. 



3. A little further forward we come to the segment of 

 mastication. There we find the motor neurones for the muscles 

 moving the jaw, and on the sensory side the large Gasserian 

 ganglion which supplies most of the head with sensory fibers, 



