AUTHOR 8 ABSTRACT OF THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE, NOVEMBER 15 



RECURRENT BRANCHES OF THE ABDUCENS NERVE 

 IN HUMAN EMBRYOS 



JOHN LEWIS BREMER 



Harvard Medical School, Boston, Massachusetts 



ONE DIAGRAM AND FOUR FIGURES 



Recurrent branches of the abducens have been known since 

 1898, and then- significance commented on by Neal, Piatt, Dohrn, 

 Belogolowy, and others. In an earher paper I showed them, 

 along with other unusual roots and branches of the abducens 

 and hypoglossal nerves. Only recently, however, have I realized 

 that in human embryos the recurrent branches of the abducens 

 are to be considered normal, instead of infrequent variations, 

 and that in man they attain their greatest frequency, size, and 

 duration. 



In many classes of vertebrates the gap along the floor of the 

 hind-brain between the most anterior roots of the adult hypo- 

 glossal nerve and the most posterior roots of the abducens is 

 more or less filled in the embryo by numerous ventral rootlets, 

 some running to join the hypoglossal, caudal to the vagus and 

 accessory nerves, some passing between the vagus and the 

 glossopharyngeal, below the upper ganglia, others taking a more 

 dorsal course, like the dorsal rami of spinal nerves, to end in the 

 dorsal head musculature. Many of these rootlets are abortive, 

 and end before their definite direction can be more than imagined. 

 They may, if they persist long enough, cause probably transient 

 foramina in the cartilaginous base of the skull, in line with the 

 hypoglossal foramina, or they may pass out by the jugular fora- 

 men. They may be connected by longitudinal strands, at a 

 short distance from their point of origin from the brain, thus 

 forming a series of loops often continuing the direction of the 

 abducens caudally toward the hypoglossal. Such a continuation 

 of the abducens caudally, or a separate caudally running root 



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THE AMERICAN JOURNAL OF ANATOMY, VOL. 28, NO. 2 



