686 THE HIGHER ANTHROPOIDS 



column and is fontinuous across the miciliiu' with its Irllow oi the opposite 

 side. 



The Dorsal Medullary Nuclei 



The first of the dorsal sensory nuclei to appear is the nucleus of GoII 

 which comes into view in the hii^hcst cervical sections. It develops as a 

 narrow prolongation extending backward from the surface ol the central 

 iirax matter close to the midline. Continuous with the dorsal surface oi the 

 central gray matter, from which it takes its origin, it rapidly increases in a 

 veiitrodorsal direction until it occupies almost the entire depth of the column 

 of Coll. It is compressed from side to side and completely surrounded, e\cei:)t 

 at its base, by the fibers of the column of Coll. As the lower extremity of the 

 fourth ventricle is approached the nucleus begins to shorten in its ventro- 

 dorsal diameter, at the same time showing a marked tendency toward the 

 formation of a nuclear outgrowth which resembles the overhanging branches 

 of a tree. As the ventricle opens the nucleus is pressed aside and separated 

 from its fellow of the opposite side. The nucleus of Coll comes to an end 

 shortly above the opening of the fourth ventricle. The nucleus of Burdach 

 appears at a level only slightly above the appearance of Goll's nucleus as a 

 dorsal prolongation from the base of the dorsal horn. This mass of nuclear 

 material increases until it occupies a large part of the column of Burdach 

 with a dorsolateral extension passing laterally and conforming to the surface 

 configuration of the medulla oblongata. This lateral swing is carried so far 

 that the nucleus of Burdach overhangs to a considerable extent the sub- 

 stantia gelatinosa trigemini w hich is separated from it by the descending root 

 fibers of the trigeminal nerve. The nucleus of Bmclach extends ujiward almost 

 to the level of entrance ol' tlu' cochlear root, bt'ing separated gradually from 

 the floor of thi' fourth \entricle by the inler\ention at this point of the 

 vestibular complex. 



