CYCLOPIA IN THE HUMAN EMBRYO. 31 



from the brain-stem of the third, fourth, fifth, and sixth nerves were symmetrical 

 for both faces. The arrangement of the nerves on the cyclopean side are as follows: 



1. The olfactory nerves are absent. 



2. The origin of the optic nerve was lost. Two small and flattened optic 

 nerves, however, pass out together in the dura. These finally fuse into one stalk 

 which ends in the bulb. This stalk, 2 mm. in diameter, is about the same size 

 as the normal optic nerves of the well-formed face on the opposite side. 



3. The two third nerves which belong to the cyclops are 0.5 mm. in diameter 

 at their point of origin and throughout their course, while the third nerves on the 

 opposite side which pass to the perfect face are twice that size. The cyclopean 

 oculo-motor nerves pass into the dura, where they run toward each other to 

 the place where the eye-muscles arise. Here these nerves lie within 3 mm. of 

 each other. Branching occurs in this region. Two of these branches fuse im- 

 mediately. There are two other pairs of main branches which innervate the 

 levator palpebrse and the superior recti on each side of the single eye. There are 

 some finer branches whose course could not be definitely ascertained. 



4. The cyclopean fourth nerves are equal in size with those of the normal 

 eye. They run as two fine threads to within a few millimeters of each other, 

 when they turn anteriorly and run parallel on the surface of the superior oblique 

 muscles, in which they terminate. 



5. The two Gasserian ganglia of the cyclops are somewhat smaller than those 

 of the normal face. Each has three divisions: ophthalmic, maxillary, and man- 

 dibular. The two ophthalmic divisions have each three main branches. One of 

 these branches passes along the roof of the orbit and makes several x-shaped 

 anastamoses with its fellow near the front of the eyeball. Another runs forward, 

 parallel with its fellow, out into the skin, where they are both cut; so if anastamosis 

 occurred it could not be determined. The third and last branch, one on each 

 side of the eye, ends in the lacrymal gland. 



6. The sixth nerves of the cyclops, about 0.8 mm. in diameter, are equal in 

 size with the sixth nerves, passing to the well-developed face. They converge to 

 the base of the orbit when they run parallel to each other on the upper side of 

 the lateral recti muscles, in whose substance they terminate after making several 

 X-shaped anastamoses. 



