CORPUS QUADRIGEMINUM ANTERIOR 49 



Plate XXIII. shows the large nerve cells of the superficial gray layer of the corpus quad- 

 rigeminum anterior. This layer appears to contain the cells which are peculiar to the corpora 

 quadrigemina. 



Two cells are shown in the plate quite different from each other. The larger cell is 

 about 60 /A in size. It has six protoplasmic extensions, from each of which several dendrites 

 are given off. These have numerous branches and radiate widely from the cell, evidently 

 passing to a considerable distance from it. There is no neuraxon visible, but other specimens 

 from this region show that these cells possess a long neuraxon which passes out of the body 

 and assumes an antero-posterior direction, entering either the optic tract or the fillet. 



The second cell shown is a triangular cell with numerous dendrites which have a very 

 large calibre, a long course in various directions, and give off a few branches in their course. 

 The neuraxon of these cells enters the visual tract and passes to the occipital cortex. 



Through the plate the enormous plexus of nerve fibres is evident, and many axis cylin- 

 ders can be seen easily separable from the dendrites by their finer calibre and straighter course. 

 Many have varicosities, but very few give off collaterals. The general direction in which the 

 majority are passing is from without inward. This- plexus belongs to the visual apparatus which 

 has been already described. 



