Chapter VIII 



RECONSTRUCTION OF THE GRAY MATTER IN THE 

 BRAIN STEM OF MYCETES SENICULUS 



MYCETES scniculus has been selected for reconstruction as repre- 

 senting the Ceiiidae. This animal shows a deiinite advance over the 

 lemur and the marmoset. In size it exceeds considerably the animals 

 already mentioned and the brain reconstruction is correspondingly larger 

 than that found in either of the two preceding forms. 



The Dorsal Sensory Nuclei 



The nucleus of Goll first appears in the reconstruction as a dorsal 

 extension of the central gray matter between the point of attachment of the 

 dorsal gray column to the central gray column and the dorsal median septum. 

 The nuclear mass is a narrow prolongation from the central gray column. It 

 rapidly extends dorsally until it forms a core in the column of Goll. The 

 nucleus is narrow, laterally compressed and presents a somewhat bulbous 

 enlargement at its dorsal tip. At a somewhat higher level than the origin of 

 the nucleus of Goll there appears on the dorsal margin of the central gray 

 column a flat, sessile condensation in the central gray column which is the 

 beginning of the nucleus of Burdach. At about the same level in the 

 dorsal portion of the mass of white fibers forming the column of Burdach 

 appear isolated masses of gray matter which coalesce and become attached 

 to the dorsal extension of the central gray column to form the external 

 nucleus of Burdach. The arboreal character of this nucleus, already mentioned 

 in lemur, is further developed in mj'cetes. 



The appearance of the nuclei of Goll and Burdach between the dorsome- 

 dian septum and the point of confluence of the dorsal gray column with the 



