Page:Proceedings of the Royal Society of London Vol 60.djvu/441

Rh roots, and to tlie skin distribution of the cranial nerves. The communication is divided into four sections. In Section I the field of peripheral distribution of eacli root is described from the Vth cervical to the lower end of the brachial region. The description given is taken in each case from one particular experiment, which has proved a typical one for the root in question, and then deviations from this type are appended to it in the form of annotations. Particular attention was paid to the question of the skin-fields of the several divisions, ophthalmic, maxillary, and mandibular of the cranial Vth, in order to see if the fields possessed the characters of segmental skin-fields, or those of peripheral nerve-trunk skin-fields. They were found to conform with the latter, not with the former. A curious relation of the posterior edge of the field of the Vth to the external ear is found to exist, indicating that the position of the visceral cleft is still adhered to as a boundary line for the field of the trigeminus. The sense of taste as well as of touch is found to be destroyed in the anterior two-thirds of the tongue after intracranial section of the V th; this makes it extremely doubtful whether the corda tympani can have gustatory functions in the monkey, as has been believed in some cases in man. No loss of eye-movements, or interference with them, has been found to result from intracranial section of the Vth.

The results obtained on the various successive nerve-roots cannot well be abstracted. The glossopharyngeal field on the tongue has been successfully delimited.

After cranial Vth and all the upper cervical posterior roots have been severed, there still persists a small field of sentient skin, which includes the external auditory meatus and a part of the pinna. This field, although not corresponding to the situation given by anthropotomists to the distribution of the auricular bra nch of the vagus, comes either from it or the glossopharyngeal. It presents interest as being the only field representing the whole cutaneous distribution of an entire nerve, which does not conform with the rules of zonal distribution Holding good in the case of each of the other nerve-roots examined, and tnese now include the whole series. The posterior root of the 1st cervical nerve has a skin-field in the cat which includes the pinna. Hie posterior root of the same nerve in Macacus has no skin-field at all, its skin-field having apparently been included in the Ilnd cervical of Macacus, not in the cranial Vth. The root fields contributing to the surface of the brachial limb are Illrd, IVth, Vth, Vlth, VHtli, and VIHth cervical, and 1st, Ilnd, and Illrd thoracic! Of these, the VHIth cervical is the only one which includes the whole of the surface of the free apex of the limb; its distribution in this respect closely resembles that of the Vlth lumbar sensory root in the pelvic limb.