264 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



section so as to lie wedged in between the axis of the brain 

 and the optic lobe. It at once turns sharply downwards 

 and forwards, and becomes closely opposed to the dorsum 

 of the oculomotorius. For some sections the two nerves 

 can be distinguished, but in front they appear to fuse 

 completely, and cannot be distinguished even under the 

 high power. The pathetic is, however, given off again 

 from the dorsum of the oculomotor, passes forwards and 

 downwards, pierces the membranous wall of the brain case 

 obliquely in front, and breaks up in the superior oblique 

 muscle of the eye as shown in the figure. 



On the left side the relations of the nerve to the brain 

 and for some distance in front are essentially the same as 

 on the right side. As, however, it approaches the eyes 

 (section 392 of chart), it begins to pass towards the lower 

 or right optic nerve Subsequently it takes up a position 

 above and to the left of the upper or left optic nerve, 

 having now crossed over the top of the parasphenoid and 

 lying distinctly to the right of the morphological middle 

 line. The two optic nerves having dipped down the left 

 pathetic crosses over the left optic to its right side. The 

 left optic now turns upwards towards its eye, so that the 

 left pathetic lies considerably below it. The latter after- 

 wards passes upwards to the left side of the frontal bridge, 

 and is seen below the right pathetic. It finally breaks 

 up in the left superior oblique in much the same way as 

 the right. 



Nervus abducen s — VI. 

 The sixth nerve (vi. r.e.), which consists mostly of 

 large well myelinated fibres together with some small 

 ones, arises from the medulla by two small rootlets some 

 distance from the middle line. Both these rootlets have 

 apparently a common nucleus situated far from the middle 



