&8 PROFESSOR A, MILNES MARSHALL, 
showing its relation to the ophthalmic branch of the fifth (v a.) 
particularly clearly. ; 
The palatine nerve is shown at stage m in figs. 15, 16, and 17 
(vir 6) ; it is a stout straight nerve, lying immediately super- 
ficial to the maxillary branch of the fifth and very close to 
this latter; these relations are still better seen in the trans- 
verse sections shown in figs. 28 and 29; in both these 
figures the two nerves (vi 4.) and (v 8.) are seen running 
down side by side, and so close together as almost to touch 
at places. 
The hyoidean branch (v1 c.) is shown in figs. 15, 16, and 18 ; 
and finally, the mandibular branch (vir d.) is well seen in 
figs. 32, 33, and 34. 
The seventh nerve is, in these stages, a very large nerve, very 
much larger than the fifth ; two of its branches, the ophthalmic 
and palatine, accompany branches of the fifth, the ophthalmic 
and maxillary, very closely indeed, the branches of the seventh 
lying in both cases more superficially. 
Finally, the seventh nerve never acquires additional non-gan- 
glionic roots of origin, such as have been described as occurring 
in both the third and fifth nerves ; this is a distinction of some 
importance and one to which I shall refer again further on. 
Comparison of the Third, Fifth, and Seventh Nerves.—In 
the section on the relations of these nerves to the head cavities 
it has been shown that the third has the same right to be con- 
sidered a segmental nerve that the fifth and seventh nerves have ; 
and that it must, therefore, be regarded as a nerve of equal 
morphological importance with the latter. It is, therefore, a 
point of considerable importance to determine how far the 
several branches of these three nerves can be compared with one 
another. 
All three nerves arise at first by single ganglionic roots; in 
the case of the third and fifth additional non-ganglionic roots 
are subsequently acquired, but in the case of the seventh no 
such roots are acquired. I hope to show shortly that this 
apparent distinction is capable of full and satisfactory expla- 
nation. 
Of the three nerves the seventh is very much the largest, the 
third very much the smallest, the fifth, which is intermediate in 
position, being also intermediate in size; this statement apply- 
ing not only to the main trunk, but to the individual branches as 
well. 
In comparing the fifth and seventh nerves, there can be but 
little doubt that the mandibular branch of the fifth corresponds 
to the hyoidean branch of the seventh; and when we bear in 
