102 LOCALIZED ELECTRIZATION. 



" The thyro-aryfsenoidetis externus (Henle), or ary-syndesmicus (Luschka 

 Merkel), which rests close against the anterior and ujiper margin of the crico- 

 thyroideus lateraHs, and also the thyro-aryt^uoideus internus, lying some- 

 what further inwards, can both be reached from the pyriform fossa. The 

 position of the electrode must be chansied, so that its point presses down- 

 wards, inwards, and forwards ; while the handle is carried upwards and out- 

 wards, towards the upi^er teeth and angle of the mouth. 



" The effect of the direct excitation of the thyro - arytsenoideus, thus 

 produced, consists only in a drawing of the arytsenoid cartilages forwards 

 and downwards. It is manifest that no tension of the vocal cords can be 

 produced, so long as the arytsenoid cartilages are not fixed inwards and 

 backwards by the arytfenoidei transversales and the crico-arytsenoidei 

 postici ; nor the thyroid and cricoid cartilages approximated by the crico- 

 thyroidei. 



" In these excitations from the pyriform sinus, in which a certain degree of 

 pressure is required, care must be taken not to confound mechanical move- 

 ments imjjressed upon the jmrts of the larynx by the point of the electrode 

 with movements resulting from muscular contraction. To prevent such an 

 error, it is necessary to study the iDosition of the aryttenoid cartilages, and of 

 the soft parts, after the introduction of the electrode, with the cii'cuit at first 

 oi^en, and then closed. 



" The two thyro-arytfenoidei interni can be reached from the glottis, by 

 placing the electrode, during insi:)iration, quickly and steadily upon, or 

 between the vocal cords. By closure of the glottis by reflex action, the 

 sponge-covered end of the electrode will be caught between either the true 

 or the false vocal cords. In the fiivst case it touches the former by their 

 margins, in the second, from above. This method of excitation is highly 

 irritating to the mucous membrane of the larynx ; and should not be often 

 repeated diu-ing one sitting. 



" The crico-arytfenoidetis posticus, the actual dilatator glottidis, lies upon 

 the posterior surface of the cricoid cartilage, on either side of a central 

 prominence. According as it is wished to stimulate the right or the left 

 miTscle, the point of the electrode must be made to glide from the arytsenoid 

 cartilage either to the right or left behind the plate of the cricoid cartilage. 

 At first the constrictor muscles offer strong resistance ; and it is sometimes 

 necessary for the i:)atient to swallow, in order that the electrode may be 

 guided to its right place. Sometimes these muscles may be excited from the 

 pyriform sinus, by carrying the electrode backwards and downwards. As 

 soon as the muscle contracts and bulges, the electrode is liable to slip from 

 its place ; so that its position should be attended to. 



" The effect is slight rotation of the arytasnoid cartilages on their axis, in a 

 direction outwards, and also movement of them backwards and outwards, so 

 that the glottis is completely opened. If the patient attempt to produce a 

 note, while one muscle only is excited, a false and deeper note is produced, 

 since only the vocal cord of the other side is brought into play. 



" The muscles of the epiglottis, which receive their nerves from the superior 

 laryngeal, namely, the thyro- and ary-epiglottidei, can be excited either 

 directly— from the lateral portions of the base of the epiglottis — or indirectly, 

 where the internal branch of the superior laryngeal nerve passes through the 

 laryngo-pharyngeal sinus. 



" The glosso-ei)iglotticus, which consists, according to Luschka, only of a 

 few terminal bundles of the longitudinalis linguae superior, in the neighbour- 

 hood of the glosso-ejiiglottic folds, can seldom require the attention of the 

 surgeon. It can be reached, from the glosso-epiglottic ligament, more easily 

 than any of the muscles that have been mentioned. 



" The vagus nerve can be reached, according to Duchenne, from the 

 oesophagus ; and, according to Semuola and Gerhardt, from the surface of the 

 neck. The first method presents many difficulties, since the operator works 

 in the dark. The second is easier, but of still more doubtful value ; since, 

 on account of the deep position of the nerve, even when the electrode is in 



