624 yournal of Comparative Neurology and Psychology. 



whose long root is shown sweeping forward in a curve at the side 

 of the medulla. Nearer the median line the roots of the hypo- 

 glossal nerve are represented at though cut off quite close to their 

 origin; and median to the otocyst is the abducens. Between the 

 anterior roots of the hypoglossal nerve and those of the abducens 

 are several rootlets, from the caudal group of which arise three 

 nerves, two running behind the vagus-accessory trunk, one point- 

 ing to the space between the vagus and glossopharyngeal nerves; 

 while from a root near the abducens, a fiber bundle runsas though 

 to join the anterior nerve just mentioned. All of these fibers have 

 a lateral course. 



med. 



Fig. 4. Graphic reconstruction of human embryo, u.5 mm. (H. E. C. series 189, sections 136 

 to 150.) X 50. a, dorsally running aberrant nerve, arising by a branch of the abducens and by three 

 ventral roots. For other lettering, see fig. I. 



On the left of the drawing the position of the glossopharyngeal 

 and vagus-accessory trunks is merely indicated while the hypo- 

 glossal nerve is represented as having been cut off lower down 

 (i. e., nearer to us) after its various roots have joined to make the 

 main trunk. The anterior root takes a lateral course at first, but 

 after sweeping well outside, turns and joins the trunk lower down. 

 The fibers just anterior to this root, however, persist in their lateral 

 course, and turn caudally to run in the mesenchyma at the side 

 of the head. Anterior to these, other fibers, still running late rally, 

 at right angles to the large nerve trunks, turn forward as two 

 small nerve bundles, pointing in front of the vagus; and from the 

 abducens a posterior branch, joined by fibers from a separate root, 

 also runs laterally toward the same space. In this embryo, then. 



