Chapter .Will 



RECONSTRUCTION OF THE GRAY MAIIER IN THE 

 BRAIN STEM OF SLMIA SATVRUS, THE ORANG-OUTANG 



Y' I ^1 IE gray niattcT m the hraiii slcni of llu' oranii;-outan<i in many 



I respects resembles that m the human. The component structures 



II have mati'riall\ uureasecl in size, their complexity is greater and the 



entire organization of the central nervous system shows a distinct ad\ance 



over the lower primate forms. 



In the high cer\ical lexels ot the spinal cord the conliguration ol the gray 

 matter is idi'iitical with that in the human cord. The central gray matter is 

 more or less cjuadrilateral in shape, connected at its ventrolateral angle with 

 the ventral gray column. Extt'iiding Irom its dorsolateral angle is tlu' narrow 

 eer\i\ ot the dorsal horn which is capped by the substantia geiatinosa 

 Rohmdi. The dorsal sensorx' nuclei ha\'e already made their aj^pearance m the 

 dorsal columns, although the distal portion ot the nucleus ot Goll is not yet 

 connected with the ct'iitral gray matter. It is represented b\ a narrow, com- 

 pressed strij) ot gra\ matti'r 1\ ing m the \eiitrodorsal plane close to the mid- 

 line, completel\ surrounded by fibers ot the column ol Goll. I he dorsal horns 

 are alread\' showing their tt'iideiicx to mo\c into a lateral position. This 

 tendency is sliow n more 1)\ the lateral inclination ol the e\tremit\ ot the 

 dorsal horn than b\ the cer\ i\. On tlu' latt'ral sick- of tht' \entral gray column 

 the ri'ticular lormation appears as a small triangular area. 



The Dorsal Sensor^' N'l clei 



The nuckais ot Goll appt'ars in the Inst k'\ els ot the reconstruction as an 

 indepeiuk'nt, com|M-essed band ot gray matter lying among the libers of the 

 column of Goll. It tiuickly establishes connection with the dorsal surface of 



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