58 THOMPSON YATES LABORATORIES REPORT 
the bregma, and just in front of a transverse line joining the highest points of the roots of the right 
and left pinna?, sweeps laterally in a rectilinear manner. Having reached a point about .5 centim, 
above the level of a line drawn from the outer canthus of the palpebral fissure to the external 
auditory meatus, and in a vertical about 13 millims. in front of the front edge of the root of the 
pinna, the boundary of the field slopes downward and forward to a point at which the following 
two lines cross : a, line from angle of mouth to top of root of pinna ; ^, line from outer canthus to 
the angle of the lower jaw. From this point it runs horizontally forward for a centimetre or 
more, and finally it ascends, sloping forward, to the free edge of the lower lid, attaining it a little 
to the lateral side of the middle point. Winding over the free edge of the lid, it continues to 
slope inwards on the conjunctival surface, and finally emerges at the inner canthus, without the 
border having invaded at all the ocular conjunctiva ; that is, the whole ocular conjunctiva is 
included in the field of the first division of the Vth. On the bridge of the nose the boundary 
slopes downward and inward, so that it reaches the crossed overlap from the field of the nerve of 
the opposite side. It was not found that the tip or any part of the lower 3 centims. of the nose 
was supplied by the ophthalmic division of the trigeminus. Abovit 1.5 centim. above the opening 
of the nostril, the internal surface of the nose, both on the septal and on the lateral walls, 
responded to touch ; these must therefore be supplied by the n/mus ophthalmicus. The hard 
palate and the greater part of the soft palate gave no response ; the extreme posterior edge of the 
soft palate certainly responded to touch ; this response persisted after final section of the whole 
trigeminus. There was distinct photophobia of the right eye, but no vascular injection and no 
abnormal degree of lacrymation. There was no obvious difference in size between right and 
left pupils.' Another experiment yielded almost absolutely identical results. 
To ascertain the field of the 2nd division {ramus maxillaris), the Ilnd cervical nerve was 
divided, and the ist and 3rd divisions of the Vth. The area of response upon the face obtained 
in this way was bounded by a line which commenced at the crossed overlap on the middle line at 
the top of the root of the nose, i.e., on the frontal bone about the level of the superior edge of 
the orbits, or about the region of the iiuman glabella. From this point the boundary sloped 
rapidly down to the inner canthus of the eye, crossing the most median portion of the upper lid 
to attain the canthus : it then ran along the conjunctiva of the inner face of the lower lid, and at 
the outer canthus crossed upward over the upper lid, so as to include in the field the most lateral 
sixth of that lid. It then turned horizontally outward over the malar prominence, and, after 
extending along a good third of tlie line from the outermost point of the orbital opening to the 
external auditory meatus, bent downward and then swept toward the angle of the mouth ; this it 
reached from below, so as to include the extreme lateral edge of the lower lip ; it runs almost 
horizontally along the inner surface of the cheek to the maxillary gums. Along the middle line, 
both at lip and nose, the crossed overlap is very small indeed. 
To delimit the 3rd division {ramus mandibularis), the following experiments were made : — 
The Ilnd and Ilird cervical roots were cut in the vertebral canal, and the ist and 2nd divisions 
of the Vth just distal to the Gasserian ganglion. The anterior boundary of the field of response 
then ran from the angle of the mouth to the anterior end of the lower border of the zygomatic 
