CHAPTER X. 

 Organs of Sense. 



SECT. I. THE EYE. The apparatus of vision com- 

 prises the globe of the eye, or the organ of sight pro- 

 perly so called ; its organ of protection, the eyelids ; 

 and its motor and lachrymal apparatus. As the two 

 latter present no features of special histological 

 interest, we shall omit their consideration. 

 Eyelids The several layers of tissue which enter into the 

 composition of the eyelids, proceeding from without 

 inwards, are : the skin, the orbicular muscle, the 

 fibrous stratum, and finally, the mucous membrane. 



The skin is exceedingly delicate, but otherwise it 

 presents the same structure as elsewhere. Situated 

 deeply in its substance, and near the free edges of the 

 eyelids, we find the hair-follicles of the cilia or eye- 

 lashes, surrounded by their sebaceous glands (PL 

 XXVII. fig. V.). The orbicular muscle of the eye- 

 lids belongs to the class of striped muscles (PL 

 XXVII. fig. II.). The fibrous stratum, very thin at 

 the bases of the eyelids, becomes more dense towards 

 their free edges, where it forms the tarsal cartilages. 

 These are composed of connecting tissue very much 

 condensed, and studded with plaematic cells. We 

 search in vain in this stratum of fibrous tissue for car- 

 tilage cells, or at least, they are so rarely encountered 

 that they cannot be regarded as constituting one of 



