_Removal of the Gasserian ganglion._ There is some divergence of opinion as to whether it is necessary to remove the ganglion entire or whether it suffices to resect the lower two-thirds--that part through which the fibres of the second and third divisions course--the upper third being left intact. This latter course is advocated by Jonathan Hutchinson on the grounds that (1) the first division is but rarely involved in the neuralgic process, (2) its inclusion in the process of removal entails some risk to the eye--conjunctivitis, keratitis, and sloughing of the cornea, and (3) resection of the lower two-thirds of the ganglion, when carried out in suitable cases, is but rarely followed by the development of neuralgia in the first or ophthalmic trunk. Added to these facts, it must be admitted that the complete removal of the ganglion is associated with added operative risk--wounding of the cavernous sinus and injury to the third, fourth, and sixth nerves. The Gasserian ganglion lies in the cavum Meckelii, a depression on the anterior aspect of the petrous portion of the temporal bone, and is situated between the two layers of dura mater, the stronger on the upper or cerebral side, the weaker between it and the bone. Under the pathological conditions often existent in cases of trigeminal neuralgia, considerable adhesion may be present between the ganglion and its enveloping coats. Consequently, its complete exposure is often a matter of considerable difficulty. The dura must be stripped away from the outer aspect of the ganglion, firstly by dividing the membrane along the border of the ganglion between the site of emergence of the second and third divisions, and then by blunt dissection. The ganglion and its efferent branches being exposed, _resection of the lower two-thirds_ may be carried out. The second and third nerve trunks are severed flush with the basal foramina, traction applied, and the lower portion of the ganglion resected. During the final stages, the manipulations of the operator are again likely to be obscured by venous oozing and by the discharge of some cerebro-spinal fluid. Patience, careful application of gauze plugs, and good illumination of the field of operation are required to overcome these difficulties. In some few cases the bleeding has been so profuse that the operation has had to be abandoned for the time being, a fresh attempt being made some days later. This course should, however, rarely be necessary. Similarly, if the operator should deem it necessary to remove the whole ganglion, this procedure may now be carried out. The posterior part of the ganglion is exposed, together with its sensory root. This root is hooked forward with a small blunt-pointed hook and then divided. Traction is applied to the ganglion and it is turned forwards, the three terminal divisions being divided one after the other with the minimum risk of injuring the cavernous sinus.