620 THE EYE. 



humour, made transversely to the axis of tne eyeball (fig.430), but whether 



there is any ])re-existent structure to account for the appearance is 



not known. It is conceivable that these appearances may be merely 



produced by the manner in which the albuminous 



substance has undergone coagulation l)y the reagent 



em])loyed. 



However this may be, there exists, nearly but 

 not quite in the axis of the eye, a definite struc- 

 ture in the shape of a distinct canal, about a 

 line in diameter, filled with fluid and extending 

 from the 2^ctpilla opt id to the back of the lens cap- 

 sule where it apparently terminates blindly. This 

 is the cmialis hialoideus or ccmal of SlUlinri. It 



FlS. 431). — lilANSVERSE • i , i • j.1 r 1 J i i 



Section of Human ^^ "^st shown m the fresh eye, and may be also 



Eye, hardened in injected by forcing a coloured solution under the 



Chromic Acid, SHOW- pia-matral sheath of the optic nerve (Schwalbe). 



iNG Radial Stri- 'yIiq canal widens somewhat towards its posterior 



ation of the \ it- l ■: n ■ 1 j? • i i t 



REous Body (after P^^'^ '• ^^s wall IS composed of an excessively dcli- 



Hannover). cate homogeneous membrane. 



Scattered about throughout the substance of the 

 vitreous humour are a variable number of corpuscles, for the most part 

 capable of exhibiting amoeboid movement and many of them apparently 

 of the nature of white blood corpuscles. Some of the cells here met with 

 are remarkable for the very large vacuoles which they contain, and which 

 distend the body of the corpuscle, pushing the nucleus to one side ; 

 the cell processes are for the most part peculiar in possessing numerous 

 little secondary bud-like swellings, or they may present a varicose ap- 

 ]iearance, like strings of pearls. Similar bodies are also found floating 

 free in the vitreous humour. IwanhofT further describes other cells, 

 especially frequent near the perijdiery, of a stellate and spindle-shaped 

 form and possessing similar processes. 



The fluid collected from the vitreous humour consists chiefly of 

 water ; it contains, however, some salts with a little albumen, in the 

 form of an albuminate of soda, and, in the human eye, also traces of 

 mucin. 



The hyaloid memhrane invests, as before mentioned, the whole of 

 the vitreous humour, except in front, where the membrane passes 

 forwards to the anterior part of the margin of the lens, becoming also 

 firmer in consistence and distinctly fibrous in structure. This portion 

 of the hyaloid is known as the zoivila of Zinn, and the suspensory J'Hja- 

 ment of the tens (fig. 431, z, 1 1). The posterior part, or hyaloid proper, 

 is exceedingly thin and delicate, and is readily thrown into folds when 

 detached. Under the microscope it presents no appearance of struc- 

 ture : but, flattened against its inner surface are generally to be seen 

 a number of granular nucleated corpuscles, which exhibit amoeboid 

 movements : they appear to be merely migrated white blood corpuscles. 

 The ciliary part or zonula, on the other hand, presents radiating 

 meridional fibres, stiff in appearance, and apparently intermediate in 

 character between elastic and white fibres of connective tissue ; they 

 commence generally about opposite the ora serrata, and confer con- 

 siderable stoutness upon this portion of the hyaloid membrane, which 

 here, as its name implies, assists in supporting the lens, to the capsule 

 of which it is anteriorly firmly attached. Moreover, this part of the 



