NERVOUS SYSTEM OF A TWO-HEADED PIG EMBRYO 425 



fasciculus longitudinalis medialis (fusion farther caudad than 

 any of the figures). Of the non-nervous structures may be 

 mentioned the terminal ends of the median submaxillary and 

 sublingual glands (figs. 18, 19), cartilages of the external, middle, 

 and internal ears of the median region (figs. 15 to 19), basis 

 cranii (figs. 14, 15), and some of the cheek muscles. All of the 

 conjoined structures receive contributions from the left half of 

 head A and the right half of head B. 



24. The dorsal quadrants of the juxtaposed halves of the two 

 heads have been the most involved in the dupUcity of the teras, 

 and all the structures immediately associated with these quad- 

 rants have shared in the altered form relations; nevertheless the 

 normal morphological and neurological pattern is clearly recog- 

 nizable, and all of the anatomical evidence points toward a 

 merely regulatory adjustment in a healthy, orderly developed, 

 though teratological embryo, for wherever normality, or near- 

 normahty, can assert itself it is anatomically reahzed or approxi- 

 mated. 



BIBLIOGRAPHY 



Ahlfeld r. 1880 Atlas zu den Missbildungen des Menschen I. Lieferung 



Tafel I-XXIII. Leipzig. 

 Barbour E. H. 1896 A two-headed tortoise. Science, vol. 4 pp. 159-160. 

 Bishop, M. 1908 Heart and anterior arteries in monsters of the dicephalus 



group. Am. Jour. Anat., vol. 8, pp. 441^72. 

 Black, D. D. 1913 On the so-called 'bulbar' portion of the accessory nerve. 



Proc. Amer. Assoc. Anat., 13th session, Dec. 30. 

 Bruce, A. 1891 On a human cyclops. Proc. Royal Soc, Edinburgh, vol. 20, 



pp. 412-421. 



1893 Illustrations of the nerve tracts of mid and hind brain and the 



cranial nerves arising therefrom. Edinburgh and London. 

 Gary, Eben 1917 The anatomy of a double pig, syncephalus thoracopagus, 



with special consideration of the genetic significance of the circulatory 



apparatus. Anat. Rec, vol. 12, pp. 177-192. 

 Ghauveau, a. 1903 The comparative anatomy of the domesticated animals. 



2nd Eng. edit., New York. 

 Ghild, G. M. 1915 Individuality in organisms. Ghicago. 

 Ghild, C. M., and McKie, E. V. M. 1911 The central nervous system in tera- 



tophthalmic and teratomorphic forms of planaria dorotocephala. 



Biol. Bull., vol. 22, pp. 39-59. 

 Cunningham 1915 Text-book of anatomy. 4th revised edit.. New York. 



THE JOURNAL OF COMP.'^BATIVE NEUROLOGY, VOL. 32, NO. 4 



