30 



CYCLOPIA IN THE HUMAN EMBRYO. 



S.ob. 



S.ob. 



Lp. 



orbits. This shows there is a true normal union for the two individuals at this 

 point. In the cranial cavity behind the Cyclopean eye one optic nerve-stalk, com- 

 posed of two bundles pressed together, is observed. 



The dome of the cranium is filled by three cerebral bodies; two of these are 

 recognizable hemispheres, though much shortened antero-posteriorly. Their 

 position is normal, behind the well-formed face. They possess well-defined but 

 shallow cortical sulci. The third cerebral division consists of a kidney-shaped 

 lobe. Its cortex is smooth, except for two or 

 three atypical creases near the poles. It lies 

 transversely across the Cyclopean side of the 

 cranial cavity with its two poles directed infe- 

 riorly, the convex portion between them strad- 

 dling the single orbit. It represents fused cere- 

 bral tissue obtained from both individuals. 



The cyclops has a well-formed eyeball to 

 which four pairs of muscles are attached; their 

 arrangement is shown in figure 7. These mus- 

 cles can be identified by their nerve-supply as 

 being the muscles of the upper and outer parts of 

 the two fused eyes. These muscles are changed 

 from their normal positions, so that they entirely 

 surround the eye. The muscles are the supe- 

 rior obliques, the levator palpebrse, the superior 

 and lateral recti. The two superior obliques 

 lie near to the midline on the superior surface. 

 Slightly lateral to these, though still on the 

 superior surface, lie the two levator palpebrse. 

 On the sides, in the place usually occupied by 

 the lateral recti, lie the superior recti, which are 

 shifted downward from their normal position 

 through an arc of 90. About the same amount 

 of shifting causes the lateral recti to lie close 

 together on the inferior surface of the eyeball. 

 The inferior oblique muscles and the medial 

 recti are completely eliminated. The inferior 

 recti are entirety absent at the bulbar end. There is a short bundle of muscles 

 underneath the proximal end of the lateral recti, which probably represents remains 

 of the inferior recti. The lacrymal glands have participated in the change of 

 position and fusion. Their tissues lie as a broad single gland-mass on the inferior 

 surface of the bulb. 



In order to be sure that the identification of the nerves passing to the muscles 

 of the cyclopean eye was made correctly, they were carefully compared with the 

 normal nerves of the eyes of the well-developed face. This comparison left no 

 doubt as to which nerves were being traced to the single eye, as the points of origin 



IE 



FIG. 7. Diagram of cyclopean eye and its append- 

 ages of the Janus monster, No. 1178 a and b, 

 from a sketch and dissection by Dr. Finney. For 

 the sake of clearness the superior oblique muscles 

 are moved forward. The cranial nerves are 

 marked with Roman numerals. S. oh., superior 

 oblique muscles; L. p., levator palpebrse; S. r., 

 superior rectus; L. r., lateral rectus; M, rudi- 

 mentary muscle-mass, probably the remains of 

 the inferior recti. It is noticed that the first 

 branch of the fifth nerve gives rise to a trunk 

 which anastamoses across the midline. The same 

 is true of the third and sixth nerves. 



