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The third model is designed to show the cerebral nerves and the 

 relation of their nuclei both to each other and to the gray matter of 

 the cord. Beginning with the lower end of the model, the dorsal and 

 lateral columns of the spinal cord have been removed so that the gray 

 matter is exposed. The dorsal horns are colored blue and the ventral 

 red. The motor nuclei are represented on the left hand side and the 

 sensory on the right. 



Just at the junction of the cord with the medulla, the ventral 

 horn, which is split off from the rest of the gray matter by the 

 decussating pyramidal fibres, divides into two parts, a medial and a 

 lateral. The medial division gives rise to the nuclei of the hypoglossus, 

 abducens, trochlearis and oculomotorious nerves, while the lateral 

 division gives rise to the motor nuclei of the spinal accessorius, vagus, 

 glossopharyngeus, facialis and trigeminus nerves. Two wires from 

 the ventral horn show this division and represent the scattered cells 

 that connect the ventral horn with the nucleus n. hypoglossi medially, 

 and with the nucleus ambiguous laterally. 



The contrast between these two groups of nerves is well brought 

 out. The nuclei of the median group lie in the floor of the ventriculus 

 quartus or aqueductus Silvius, along the course of the fasciculus longi- 

 tudinalis medialis. The root fibres all pass directly ventralward and 

 emerge near the median ventral line, except these of the N. trochlearis 

 which pass dorsal ward, decussate in the velum and emerge near the 

 dorsal median line. On the other hand the lateral group of nuclei lie 

 farther ventralward and the root fibres of all except these of the N. 

 trigeminus make an arch in passing outward. That is to say the 

 fibres pass first inward and dorsalward and then turn veutralward and 

 outward to emerge in the lateral line. 



On the right hand side of the model are shown the sensory cerebral 

 nuclei. The nuclei funiculi gracilis et cuneati, which lie in the path 

 of the dorsal fasciculi represent the sensory nerves of the spinal cord. 

 The posterior horn as it is in the cord is shown in the cross section ; 

 in entering the medulla, the horn or the substantia gelatinosa Rolandi 

 swells and becomes the nucleus of the N. trigeminus. This nucleus 

 extends as far as the pons where the root bundle of the nerve enters. 

 The fibres of the root bundle divide into short ascending branches 

 which enter the anterior end of the nucleus, and into long descending 

 branches making the tractus spinalis n. trigemini which extends along 

 the lateral border of the nucleus as far as the spinal cord. 



The sensory parts of the glossopharyngeus and vagus nerves are 

 clearly shown as well as their relation to the motor part. The sensory 



