182 



HUMAN EMBRYOLOGY AND MORPHOLOGY. 



in front with the basis of the cornea ; behind, it is continuous 

 with the mesoblast of the vitreous humour (Fig. 148). 



conjunctiva 

 epiblast 



outer or \ 

 pigment layer] 



inner layer 

 of retina 



Vitreous 



hyaloid art.-lc 

 optic nerue- 



mesoblast 



epithet, of cornea 



basis of cornea and 

 capsule of lens. 



lens. 



lentic. cavity 



uvea 



pigment layer 

 of retina 



optic fibres / inner ,ct ^ er °f retim 

 ( basis of middle and outer 

 I tunics of eyeball 



Fig. 14S. — Diagrammatic Section of the Eye showing the Parts formed from the 

 Mesoblast. (After His' Model of the eye of a 3rd mouth human embryo.) 



(2) The vitreous humour. — This is formed out of the mesoblast 

 which fills the optic cup behind the lens. The closure of the 

 choroidal fissure cuts the vitreous humour off from the mesoblast 

 which covers the outer layer of the optic cup and becomes trans- 

 formed into the tunics of the eyeball. The vitreous humour — 

 like Wharton's jelly of the umbilical cord — represents an early 

 form of embryonic tissue. It consists of cells imbedded in a 

 jelly-like matrix. All the connective tissues of the body are 

 originally of this type, and remain as such until the fifth month 

 (Berry Hart). 



(3) The hyaloid artery. — This is the vessel which supplies the 

 mesoblast of the optic cup ; it terminates in the capsule of the lens 

 (Fig. 148). In the 7th month foetus a trace of the artery can 

 still be seen passing through the vitreous humour from the optic 



