CHAP. XVII.] 



TUBES OF THE CORNEA. 



19 



Fig. III. 



A ~-^~ 



ture, passing from one to the other, and making it impossible to 

 trace any one lamella over even a small portion of the cornea. The 

 resulting areolse, which in the sclerotic are irregular, and on all sides 

 open, are converted in the cornea into tubular spaces, which have 

 a very singular arrangement, hitherto undescribed. They lie in 

 superposed planes, the contiguous ones of the same plane being for 

 the most part parallel, but crossing those of the neighbouring 

 planes at an angle, and seldom communi- 

 cating with them (fig. 110). The arrange- 

 ment and size of these tubes can be shown 

 by driving mercury, or coloured size, or air, 



into a small puncture made in the cornea. 



They may also be shown under a high 



power by moistening a thin section of 



a dried cornea, and opening it out by 



needles. The tissue forming the parietes 



of these tubes is membranous rather than 



fibrous, though with the best glasses a 



fibrous striation may be frequently seen, 



both in the laminae separating the different 



series of tubes, and in that dividing those 



of the same layer from each other. By 



acetic acid, also, the structure swells, and 



displays corpuscles resembling those ap- 

 parent in the white fibrous tissue. Such 



is the lamellar structure of the cornea, 



which makes it so much easier to thrust 



an instrument horizontally than vertically 



into its substance. The tubes or elongated 



spaces of which we have spoken, are not 



distended with any fluid, but are merely 



moistened in the same way as the areolae 



of ordinary areolar tissue. A perfectly 



fresh and transparent cornea is rendered ^ T vV -L? ? 



opaque by pressure, but it regains its bril- ~^<^J~ 



liance on the removal of the compressing 



,, j i_ i A> Vertical section of the Human 



lorce. oO me have Supposed thlS tO result Cornea, a. Conjunctival epithelium. 



,, , . f n ' -i n -L , 6. Anterior elastic lamina, from which 



from the expulsion of fluid from between there pass off a number of fibres into 



.., . -i,,!,,! -, c, the layers of the cornea proper, 



its laminae; but that the Opacity IS OWing among which the nuclei are apparent. 



, , , , d Posterior elastic lamina, e. Pos- 



simply to a derangement of the elementary terior epithelium. Magn. so diam. 



n ., 1 . B. The posterior epithelium, o, seen 



parts OI itS Structure IS plain trom the in section ; p, seen in face.-^-Magni- 

 j, , , , fled 300 diameters. 



tact, that the same phenomena are exhi- 



c 2 



