THE SEAT OF POLL-EVIL 115 



furrow, however, although not an inoperable area, owing to the 

 fact that the vessels and nerves lie within the depth of the furrow, 

 considerable care is necessary on account of the serious consequences 

 liable to attend injuries to these structures. 



The auricular branch of the first spinal nerve passes forwards and 

 upwards ; and this nerve, as it leaves the atlas, is well protected by 

 the tubercle-like anterior extremity of the ridge which forms the 

 outer boundary of the atlantal wing. 



The outer edge of the wing is easily located in the living animal^ 

 and it is distant .5 of an inch from the antero-external foramen, so 

 that small fractured pieces of the anterior end of the edge of the 

 wing may be removed with little danger of injury to the structures 

 lying in the furrow. 



When the operation area is situate in the posterior half ot the 

 atlas, less care is needed, the only situation to be avoided being the 

 posterior foramen, since it gives passage to the retrograde artery. 

 Between the two posterior foramina we have thus a safe area, fully five 

 inches in breadth, and as the foramen is placed two inches from the 

 outer border of the wing of the bone, a large fractured portion of 

 the posterior half of the wing may be removed without any danger 

 of injuring the artery. 



In such an operation it is necessary to separate the parotid gland, 

 which is loosely attached to the outer border of the wing, an incision 

 into the substance of the gland being avoided, otherwise a fistula 

 of the gland is a liable consequence. 



