HYOVERTEBROTOMY. 459 



muscle will involve possible danger to the posterior auricular ar- 

 tery, and the risk of the division of the facial nerve. 



In rohat direction must the sharp edge of the bistoury be 

 turned? 



The reply to this is the jyohU of minhmmi danger from irregu- 

 lar motions of the instrument, caused by the struggling of the 

 patient ; and this result is most likely to be accomplished by carry- 

 ing the bistoury towards the tuberosity of the hyoid bone, and 

 consequently in the direction of the patient's nose. With the 

 instrument turned towards the ear, there would be j)0ssible dan- 

 ger of dividing the posterior auricular artery, the facial nerve or, 

 perhaps, the internal carotid. 



In carrying it tow^ard the atlas, the internal carotid, and the 

 nerves surroimding it, would be the endangered j^arts, if any. If 

 directed do\\'nward, toward the larynx, a division of the great hy- 

 poglossus, and possibly of the external carotid, might be possible. 



What must be the direction of the instrument ? 



If the bistoury is pushed through the occipito-hyoideus muscle, 

 and in a direction perpendicular to it, there will be great danger, 

 at a certain depth, of reaching and penetrating through the in- 

 ternal carotid artery ; but if an obHque direction be given to the 

 instrument, not only is this danger avoided, but no accident be- 

 yond some slight muscular injury, of no importance, need be ap- 

 prehended. 



Where is the cotinter-openi?ig to be made? 



The right place will be the most dependent part of the pouches, 

 and the instrument used must be either the S probe or the trocar, 

 as will be hereafter described. 



These preliminary points being understood, we shall the more 

 intelligently follow the description of the three steps of the opera- 

 tion, which we now proceed to give. 



1st. The Incision of the Skin and Dissection of the Posterior 

 Border of the Parotid. — This incision is made a little in front of 

 the transverse process of the atlas. It includes the skin and some 

 subcutaneous aj)oneurotic fibres, and extends to the posterior bor- 

 der of the parotid, which is at this point exposed. With the 

 straight bistom-y and dissecting forceps, the parotid border is 

 dissected, and under it the aponeurosis of the levator-humeri is 

 divided. The finger is then pushed between the aponeurosis and 

 the small oblique muscle of the head, in order to reach the occipito- 



