420 MABEL BISHOP 



Sonic of tho above interpretations of intercranial fibers of the 

 median region may seem too speculative, but with a knowledge 

 of the normal segregation of nerve fibers into dorsal and ventral 

 quadrants, and recognizing the spatial separation of the two 

 cranial nerve-masses plus the certain identification of some of 

 the nerve components in each, by elimination and analogy 

 the speculations on the remaining median nerves and their asso- 

 ciated fiber tracts are after all rather closely guarded. 



ACKNOWLEDGMENTS 



The present intensive study of the nervous system was pre- 

 ceded by a general investigation of this and other terata and 

 of normal embryos. These studies were carried on in several 

 places and at irregular intervals, and I wish to express my appre- 

 ciation of Profs. H. H. Wilder, F. P. Mall, Geo. L. Streeter 

 A. S. Warthin, G. C. Huber, and F. R. Lillie, who, by extending 

 to me the courtesies of their laboratories or by the loan of material 

 have made possible the studies leading up to the investigation 

 here recorded. I take pleasure in giving special mention to Dr. 

 Geo. W. Bartelmez, who has been most generous in giving his 

 time and kindly interest to the embryological findings in this 

 paper. 



The study of the nervous system has been made under the 

 guidance of Prof. C. Judson Herrick, of the anatomical depart- 

 ment of the University of Chicago. To him I feel especially 

 indebted, for his kindly attitude has been a constant stimulus 

 to further research and his assistance in neurology of inestimable 

 value. 



SUMMARY 



A detailed study has been made of the nervous system in a 

 laterally symmetrical dicephalous pig embryo 22 mm. in length, 

 and the following data determined: 



1. The foreparts of the two head members diverge from the 

 median sagittal plane at the same angle, but the right member 



(A) is tilted downward somewhat more than the left member 



(B) and the whole head is twisted slightly to the left (figs. 1, 2, 3). 



