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affected by the torsion of the head, since the parasphenoid 
and its eye muscle canal are simply rotated en bloc to the 
right along their longitudinal axes. The distribution of 
the nerves is therefore the same, except that those of the 
left side have been swung upwards so as to he nearer the 
dorsal edge of the body, and hence above those of the right 
side. In the case of the branch to the inferior oblique 
this rotation has caused the left one to be situated at first 
much above the right. In front, however, it begins to 
turn downwards towards the parasphenoid, and the right 
one at the same time rising, they eventually take up cor- 
responding positions at the sides of the parasphenoid and 
ethmoid cartilage. Finally the left turns upwards to 
reach its muscle in which it breaks up in much the same 
way as the right. Neither of the long eye muscle nerves 
(patheticus and the branch just described) of the left side | 
reaches, at its final distribution, a much higher transverse 
level than that of the right. 
If a comparison be made with the eye muscle nerves 
of Menidia, as described by Herrick, it will be seen that 
in the two forms the relations of the nerves are essentially 
the same. 
Nervus patheticus s. trochlearis—lIV. 
The fourth nerve of the right side (iv. 0.s.) consists of 
many large and a few small fibres all heavily myelinated. 
It has no connection with the communis vii. as described 
by Herrick in Menidia. The nucleus of the pathetic is 
situated dorsally close behind that of the oculomotor. The 
two pathetic nerves cross over the mesocoele as in all 
hitherto investigated vertebrates, so that, for example, the 
right nerve arises from the left side of the brain. The two 
nerves pass first backwards, then rise sharply over the 
mesocoele, cross, and leave the brain almost in the same 
