84 



THE OPERATION FOR ROARING. 



laryngeal cavity, and carry the incision forwards on the 

 median line to the body of the thyroid cartilage. 



Detach the slotted piece from the laryngeal retractor (Fig. 

 4) and insert the closed retractor into the incision through 

 the ligament, the ratchet end of the speculum being directed 

 toward the trachea, the curved spurs on the jaws of the 

 retractor resting within the cricoid ring. Open the dilator 

 to the full extent of the crico-thyroidean space. Insert the 

 hook of the slotted piece into the cavity of the thyroid 

 cartilage and secure in position by means of the thumb screw. 



Illuminate the cavity of the larynx. In the standing 

 animal, when facing good light, the natural illumination 

 suffices. The illumination may be improved with the aid 

 of a hand mirror. 



Excellent illumination is always available by means of a 

 reflecting electric lamp. With a good lamp the illumination 

 may be perfectly controlled in a dark room or in the dark- 

 ness of night. When the animal is cast and turned upon 

 his back, the light rays should enter the larynx from above 

 obliquely downward and forward. If the operation is being 

 done in the open field by sunlight, the patient's head should 

 be directed away from the sun, or good illumination fails. 



Observe the motion of the arytenoid cartilages, and 

 determine, if not previously done, whether the unilateral or 

 bilateral operation is to be performed. Inject into the 

 larynx and laryngeal ventricle or ventricles a sufficient 

 quantity of a solution of cocaine and adrenaline to blanch 

 and anaesthetize the mucosa. The ventricles are more con- 

 veniently injected if the syringe nozzle is bent near the tip. 



The ventricles commonly contain some mucus, which 

 interferes with the securing of the mucosa and should be 

 taken up and removed by means of a small piece of absorbent 

 cotton pressed into the ventricle with the long curved dres.s- 

 ing forceps. 



When the ventricular mucosa has been effectively anaes- 

 thetized introduce the burr into the ventricle and draw the 



