ORGANS OF SENSE. 181 



outwards towards its border wliicli it doubles, and 

 returns upon its opposite surface, where it terminates ; 

 its two faces do not give the same measurement in 

 length, which is explained by the fact that its extre- 

 mities are both beveled, and in opposite directions. 



Neither the crystalline lens nor its capsule possesses 

 vessels or nerves, at least in the" adult. During foetal 

 life, the branch of the central artery of the retina, 

 which traverses the tubular canal in the vitreous 

 humor, furnishes branches which encircle the capsule, 

 and afterwards lose themselves in the pupillary mem- 

 brane, where they anastomose with the^ciliary arte- 

 ries. 



The histological development of the eye follows Development. 

 the universal law; all of its component parts take 

 their origin from embryonic cells which take on 

 determinate metamorphoses in order to form each of 

 its individual tissues. Each of the prismatic fibres of 

 the crystalline lens is the result, apparently, of the 

 .elongation of a single cell, and not of the fusion 

 together of an indefinite number of cells. 



SECT. II. THE EAE. The skeleton of the external External ear. 

 ear is osseous in the deep portion of the meatus, but 

 elsewhere it is fibro-cartilaginous. The integument 

 by which it is invested contains glands of different 

 kinds in its several regions. In the concha we find 

 a great many sebaceous glands ; we encounter these 

 organs again in the external meatus, but here they 

 are in company with ceruminous glands ; finally, 

 sudoriparous glands are found everywhere, but prin- 

 cipally upon the internal surface of the concha. 



There is nothing especially worthy of notice in the 



