1892.] On the Mechanism of the Closure of the Larynx. 329 



base of the tongne, with or without the intervention of the epiglottic 

 base. The movements of the arytenoids constitute a gathering up 

 of the back and side boundaries, while its front boundary is virtually 

 gathered up by its remaining stationary against the base of the 

 tongne while the whole larynx moves forward. This is why swallow- 

 ing is so often but little affected by the loss of the epiglottis by 

 disease, accident, or experiment. Even loss of the arytenoids by 

 disease does not seem to necessarily cause difficulties in deglutition. 



I think it more than probable that there are differences between 

 various species, and even between individuals of the same species, as 

 to the importance of the part played by the tongue in closing the 

 larynx. This seems to follow from the very various anatomical dis- 

 positions of the parts, and may account for much of the difference in 

 the symptoms and signs of a particular laryngeal lesion in different 

 individuals. In one case a lesion of the arytenoids or ary-epiglottic 

 folds is not followed by difficulties of swallowing, while apparently 

 the same, or even a less, degree of the same lesion in another case 

 is followed by almost total inability to swallow, at all events, liquid 

 food. For instance, in John Reid's experiments of cutting all the 

 four laryngeal nerves in four Rabbits, two continued to take milk and 

 two refused it. Two Dogs similarly treated continued to take both 

 solids and liquids. In none of these cases was food found in the air 

 passages after death. Reid therefore concludes that " the epiglottis 

 . . . can prevent the ingress of food into the larynx when the 

 movements of all the muscles which diminish the size of the glottis 

 (sic) have been suspended by section of the laryngeal nerves." (" An 

 Experimental Enquiry into the Function of the Eighth Pair of 

 Nerves," 'Edinburgh Medical and Surgical Journal,' January, 1838.) 



This same forward and upward movement of the larynx brings 

 the lamina of the cricoid cartilage away from the back wall of the 

 pharynx, and so provides the room necessary for the passage of the 

 bolus. When the arytenoids are in position forwards, their highest 

 points are their margins bounding the mesial fissure. This fissure 

 thus traverses, as it were, a little ridge from before backwards, and 

 from this ridge the top of the closed larynx slopes downwards at the 

 sides and posteriorly, but especially at the sides. 



Thus, when the laryngeal entrance is closed as for deglutition there 

 is a fairly even surface for the bolus to glide over, from the laryngeal 

 face of the epiglottis to the posterior surface of the arytenoids and 

 lamina of the cricoid, and so into the gullet. 



According to this account of the closure of the laryngeal entrance, 

 the arytenoids enclosed in their mucosa an arytenoid valve or flap 

 take the place of the epiglottis according to the old account, which is 

 now all but universally discredited. 



I have KO doubt that the apparent fitness of the epiglottis as a lid 



