SECT. 226.] 



FIBRES OF MULLEK. 



561 



Fig. 231. 



/. 



cannot be followed further than the inner granular layer, and are 

 completely lost to view in the more internal strata. The thickness 

 of the different layers of the yellow spot is the following : layer 

 of the nerve-cells, 0-045"' to 0-052'"; finely granular gray layer, 

 0-020"'; inner granular lamina, 0-026'"; intermediate granular 

 lamina, 0-039'" ; outer granular layer, 0-026'"; cones, 0-030'". 



Besides the expansion of the op- 

 tic nerve, there exists in the retina 

 another remarkable system of fibres, 

 the Mullerian or radiating fibre 

 system, which was first discovered in 

 185 1 by //. Miiller in the eyes of 

 animals, and, in the following year, 

 was shown by myself to be present in 

 the human retina also. 



Proceeding from the bacillar layer, 

 in the description of the fibres of 

 Mailer, it is to be stated in the first 

 place, that every cone, and every 

 rod is connected with the elements 

 of the granular layer. With re- 

 gard to the cones, every cone- 

 granule, which is to be regarded as 

 a cell-body, is continued inwards by 

 a fine pale filament, 0-0004"' to 

 p-ooo6'" in breadth, which, after it 

 has traversed the out 

 layer and the intermediate granular 

 lamina, terminates in the inner granu- 



/( 



Elements of the bacillar layer in connec- 

 r granular Hon -with the fibres of Miiller. From the 



a granule of this layer (fig. 231, 1,/). 

 The rods also are connected in a 

 similar manner with the outer and 



human retina, magnified 350 times. 1 . 

 cones, with fibres of Miiller; a. thicker 

 part of the cone, or proper cone; b. rods 

 upon the same, one longer than the other ; 

 c. circular line at the inner end of the 

 lar laver, becoming Connected With cone; d. nucleated swelling (cell-body) of 



the same already in the outer granular 

 layer; e. fibre of Miiller, into which it is 

 continued ; e. lateral process from one of 

 these fibres, passing inwards; /. granule 

 (cell) of the inner granular layer ; g. inter- 

 nal termination of the fibre of Miiller. 2. 

 rods with Mullerian fibres; a. rod; 6. 

 inner granules, tllOUgh they present transverse line at its inner extremity; c. 



. . . commencement of the filament of Miiller ; 



SOme peculiarities lU tlllS respect. &. granules of the outer granular layer, 



. „ , -■ one seated close to the rod; e. fibres of 



Onlv a Small portion Ot the rOClS, Mvllerin the intermediate granular layer; 

 . , , . , i -, • /. inner granules;/, one of them with a 



indeed, IS COnilCCted at ltS inner CX- lateral process: r,. internal extremities of 

 .. ,, ... , the fibres of MUUer. 3. an inner granule, 



tremitV direct! V With a granule a, TMh three processes, of which the ex- 

 ,_ ix • ,1 c ii ternal one gives off branches, and supports 



(fig. 231, 2, (/) ill the maimer Ot the several other granules, b, together with 

 „ , , c . 1 rods, of which only one is figured. 



cones ; for the greater part ot them 



are first prolonged into a point (see above), which, after a course 

 of 0002'" to 0003'", passes into an extremely delicate filament, 



o o 



