DEVELOPMENT OF THE EYE. 



as a septum projecting inwards from the forepart of the choroid coat, between the lens 

 and the cornea. 



Fig. 493. 



pa-J, 



Fig. 493. VERTICAL LONGITUDINAL SECTION 

 OP THE EYE OF AN EMBRYO CALF (from 

 Kolliker). 



c, the cornea ; cc, conjunctiva of the cornea ; 

 I, the lens ; y, vitreous humour ; r, retina ; 

 p, pigment-layer of the choroid ; s c, com* 

 mencement of the sclerotic and choroid coats; 

 m, superior and inferior recti muscles ; pa, 

 folds of integument forming the commence- 

 ment of the upper and lower eyelids. 



The crystalline lens in the foetus is sur- 

 rounded by a highly vascular tunic, supplied 

 by a branch of the central artery of the 

 retina, which passes forwards in the axis of 

 the globe, and breaks up at the back of the 

 lens into a brush of rapidly subdividing 

 branches. The forepart of this tunic, ad- 

 herent to the pupillary margin of the iris, 

 forms the pupillary membrane by which 

 the aperture of the pupil is closed. The 



whole tunic, however, together with the artery which supplies it, becomes atrophied, 

 and is lost sight of before birth in the human subject, although in some animals it 

 remains for a few days after. According to Kolliker, the anterior chamber is formed 



m sc 



Fig. 494. 



Fig. 494. BLOODYESSELS OF THE CAP- 



SULO-PtJPILLARY MEMBRANE OF A 



NKW-EORN KITTEN, MAGNIFIED (from 

 Kolliker). 



The drawing is taken from a prepara- 

 tion injected by Tiersch, and shows in 

 the central part the convergence of the 

 network of vessels in the pupillary 

 membrane. 



only a short time before birth by the 

 intervention of the aqueous humour be- 

 tween the iris and cornea. 



The eyelids make their appearance 

 as folds of integument, subsequently to 

 the formation of the globe. AY hen 

 they have met together in front of 

 the eye, their edges become closely 

 glued together and they again open 

 before birth. 



The lachrymal canal may be regarded as a persistently open part of the fissure 

 between the lateral frontal process and maxillary lobe of the embryo (See p 65 and 

 fig. 56 B, 4, 6.) 



3 c 2 



