Chapter XI 



RECONSTRUCTION OF THE GRAY MATTER IN THE 

 BRAIN STEM OF PAPIO CYNOCEPHALUS 



T 



■^HE reconstruction of the brain stem of Papio cynocephalus begins 

 in the lower medullary region. The higher levels of the spinal cord 

 are not represented in the model. 

 In the lowest levels of the reconstruction the contour of the central 

 gray matter is already considerably flattened from before backward and 

 drawn into an almost directly lateral position. The central gray matter 

 gives rise at its dorsolateral extremities to the flattened cervix of the dorsal 

 horn which expands at its termination into a more or less oval-shaped 

 substantia gelatinosa trigemini. This structure has already assumed its 

 lateral position which it maintains throughout the rest of its extent. 



The Dorsal Medullary Nuclei 



The nucleus of the column of Goll consists of a narrow, laterally 

 flattened ribbon of gray matter projecting dorsally from the body 

 of the central gray matter. It is separated from its fellow of the opposite 

 side by a thin investment of white matter. The nucleus continues ccphalad 

 for some distance without showing any material change until the caudal 

 extremity of the inferior olivary nucleus is reached, when it rapidly 

 expands, presenting a heavy mass of overhanging gray matter which is 

 directed laterally under the influence of the opening of the fourth ventricle. 



The nucleus of the column of Burdach makes its first appearance 

 just below the level at which the nucleus of the column of Goll begins its 

 rapid increase in size, as a thickened condensation in the dorsal surface of the 

 central gray matter. This small mass of gray matter rapidly increases 

 in size, expanding dorsally and laterally into a relatively rich arborescent 



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