ORA SERRATA AND PARS CILTARIS. 291 



According to my observations made on fresh human eyes 

 which had been preserved for twenty-four hours, or for a some- 

 what longer period, in solutions of perosmic acid of various 

 degrees of concentration, the cells of the pars ciliaris offer very 

 diverse appearances. In general they form elongated prisms 

 resembling tall columnar epithelial cells. At their outer ex- 

 tremities they are smoothly truncated, and are in contact with 

 a pigment cell ; at their inner extremities they either become 

 enlarged or attenuated, and cleave firmly to the surface of the 

 vitreous, which is here distinctly fibrous (zonula Zinnii). 

 Many of these cells here terminate distinctly as radial sup- 

 porting fibres of the retina, presenting either a conical enlarge- 

 ment, or undergoing division ; each of the branches again 

 ceasing abruptly like a column upon its pedestal. Other cells 

 intercalated between these reach the surface of the vitreous by 

 a pointed extremity, or break up into fine fibres, so that it ap- 

 pears as though the ends pass into the fibres of the zonula. I 

 have never, however, observed a direct transition of the one 

 into the other. The whole surface of the cells of the pars cili- 

 aris is not unfrequently beset with fine elevations and rough- 

 nesses, those of the adjoining cells interlocking with each other. 

 The substance of the cells is not homogeneous, but appears 

 finely striated longitudinally, though not divisible into fibres. 

 Their nucleus is oval, hyaline, relatively large, very pale, like 

 the nuclei of the radial supporting fibres, and is sometimes 

 placed nearer to the one end, and sometimes to the other. 

 Small quantities of dark-brown granular pigment are not un- 

 frequently found in the substance of the cells, which is most- 

 closely disposed towards the exterior, so that it is doubtful 

 whether these are peculiar pigment cells (the pigmentary layer 

 of the retina), or whether the pigment cells themselves have 

 not grown out in a fibrous manner. Upon the whole, that 

 view appears to me to be the most correct, according to which 

 the cells of the pars ciliaris correspond to the radial supporting- 

 fibres. They agree generally in the nature of their substance, 

 which is in both cases finely striated, and, as it were, fibrillated; 

 in the form and refractive properties of the nucleus ; in their 

 relation to perosmic acid, which confers upon both a clear 

 brownish colour, whilst the adjoining vitreous becomes of a 



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