326 Mr. K. J. Lee on the Visual Organs of the Mole. [Apr. 28, 



On raising the anterior lobes gently from the base of the skull, it was 

 ascertained that no nerves connected the brain with the bone anterior to 

 the fifth pair. The base of the brain also exhibited an entire absence of the 

 optic nerves beyond a vestige in a very minute chiasma, as described by 

 Mr. Solly. 



On examining the internal surface of the base of the skull, the usual 

 foramina for the optic nerves are found to be wanting, a condition which 

 is observed with facility in the dried specimens in the Museum of the 

 Royal College of Surgeons. Among these there is one in which there is a 

 vestige of an optic foramen on the left side of the head, while on the oppo- 

 site side the surface is smooth and perfect. 



In the arrangement of the details which have been given above of the 

 appearances observed in the course of the examination, attention has been 

 directed to three points in particular, namely to the condition of that part 

 of the optic nerve which is situated externally to the skull, and which 

 exists as a mere thread of connective tissue ; secondly, to the eye itself, 

 and the structures within, so far as it was necessary to consider them in 

 their efficiency for optical purposes ; thirdly, to the internal surface of the 

 skull in its relation to the part of the brain from which the optic nerves 

 take their origin. 



The following description of the various structures in the foetal Mole 

 will be more general than the above account of them in the full-grown 

 Mole, as five specimens instead of one were examined. 



On the removal of the skin and a layer of muscular tissue subjacent, a 

 part of the globe of the eye is exposed. When the whole side of the face 

 and the temporal region are dissected, the eye is found to be in close 

 proximity to the large branch of the facial nerve, as is represented in the 

 drawing accompanying this account. 



The eye has the usual appearance presented by the organ in most foetal 

 mammalia ; in form globular, and in size proportionate to the head of the 

 animal ; the cornea translucent ; the sclerotic perfectly distinct, and of 

 dense white tissue ; the iris apparent through the cornea, with a clear 

 pupillary aperture. 



Between the eye and the facial nerve a small portion of the optic nerve 

 is seen in the superficial dissection, and appears to form an upright peduncle 

 for the globe. 



It is necessary to divide the seventh pair in order to examine the deeper 

 parts of the orbit. When the dissection is completed, and the optic nerve 

 exposed in its whole extent, from the eye to the base of the cranium, the 

 branches of the fifth pair of nerves are brought into view. The main 

 branch of the second division of the fifth nerve lies a little below the optic 

 nerve, parallel with it, and supplies large and numerous branches to the 

 anterior part of the face. There is no necessity to describe minutely the 

 appearance presented in the deep dissection of the orbit, as I observed 

 nothing unusual to require particular notice. There are some minute 



