152 Roaring in Horses. 



First Stage. — With a scalpel, an incision of from four to 

 six inches in length is made through the skin in the 

 middle line of the larynx and trachea, opposite the posterior 

 border of the lower jaw, extending from the body of the 

 thyroid cartilage to the second or third tracheal ring. This 

 exposes the subscapulo-hyoid, sterno-hyoid, and sterno- 

 thyroid muscles, which are incised to the same extent, and 

 as close as possible at their line of junction (raphe) in the 

 middle, the section being carried clean through to the 

 larynx and trachea. There is a variable amount of ha3mor- 

 rhage now to contend with : this, if only oozing, may be 

 checked by sponging dry until blood has ceased to flow ; 

 and if from twigs of arteries or veins, these may be seized 

 and twisted, or ligatured. 



Second Stage. — The middle cricoid- thyroid ligament, 

 cricoid cartilage, and one, two, or three tracheal rings are cut 

 through in a straight line, exposing the interior of the 

 larynx and trachea. If any blood-vessels are cut, these 

 should be taken up. A retractor (Fig. 18) is applied to 

 each side, and, these being pulled gently apart by an 

 assistant, there is ample space to manipulate in. The 

 convex lower border of the arytsenoid on each side can now 

 be seen, and if respiration is deep, that next the operator 

 (the right) will be observed to move actively from the side 

 towards the middle; while if the Eoaring is due to paralysis 

 of the left dilator muscle, there is no movement in the 

 opposite cartilage. When the breathing is very tranquil, 

 which is often the case, the right cartilage moves almost 

 imperceptibly, and it is then necessary to ascertain Avhether 

 the left one is really immovable. This can be done by 

 passing the finger, or a long probe, up towards the 

 epiglottis, when swallowing will be excited, during which 

 act the right arytasnoid cartilage is energetically jerked 

 into the middle of the cavity : but the left one does not 

 stir, or only feebly, depending upon the degree of wasting 

 of the constrictor muscles on that side. 



