GIO 



THE EYE. 



fibrils of the nerves. A direct connection of these inner processes with 

 the out\Yarclly extending branches of the large nerve-cells of the gan- 

 glionic layer has never been completely substantiated ; but it is con- 

 sidered probable that some of them may be so connected, while others 

 may pass directly to the nerve-layer and there become continued into a 

 nerve-fibre. The outer prolongation or process of the bipolar cell is on 

 the other hand thicker than the inner one, and, moreover, after a longer 

 or shorter course, divides into branches. This division commonly occurs 

 just beyond the limit of the inner nuclear layer, immediately within the 

 succeeding (outer molecular) layer ; frequently it is into two, which pass 

 off almost" at a right angle. The further destination of these branches is 

 unknown, but they are believed to break up into exquisitely fine fibrils, 

 forming a plexus in this situation. The outer process differs further 

 from tiie inner in not exhibiting varicosities ; occasionally it has a finely 

 o-ranular appearance. These cells have sometimes, but rarely, been 

 observed to possess more than two such processes (Ritter, Hulke). 



The relative length of the inner and outer process naturally differs according to 

 the position of the individual cell in the nuclear layer ; if the ceU is near the 

 inner molecular layer the outer process will have a longer course to reach the 

 outer molecular layer, and. conversely, if the cell is near the latter ; in almost all 

 cases, however, the inner process is the longer of the two, extending, as before 

 mentioned, for some distance into the contig-uous molecular layer. At the macula 

 lutea these processes or fibres of the inner nuclear layer have a markedly oblique 

 direction, in other parts of the retina they run vertically towards the sui-faces. 



The third kind of " inner granule " is entirely different from the 

 other two. The cells, each of which has a distinct nucleus and nucle- 

 olus, are exclusively collected at the innermost part of the inner 

 nuclear layer, where in man they form an almost complete stratum 

 (Vintschgau). They appear to \)Q devoid of processes, but further 



investigations are re- 

 Fig. 421. quired as to their 



nature, as well as 

 Avith regard to certain 

 other cells {fonrih 

 variety) which are 

 scattered here and 

 there in the ouler- 

 «20.s/part of the layer, 

 next to the outer 

 molecular layer, and 

 are distinguished 

 from th.e ordmary 

 " inner granules " by 

 their rounded form 

 and larger size, and 

 also, according to W. 

 Krause, in possessing 

 only one process — an 

 inner one — which he 



Fis 



421.— Branched Cells with the Uniting Feltwork 

 OF Fibres from the Outer Molecular Layer of 

 THE Horse's Retina (Schwalbe). Highly Magnified. 



regards as a terminal nerve-fibre. 



5. Outer molecular layer.— The outermolecularlayerismuch thinner 



than the inner, but otherwise presents, in vertical sections of hardened 



