EXPERIMENTS OF WYLLIE. 627 



Morgagni when the glottis is closed, inasmuch as these are 

 simply oblong orifices in the lateral walls of the larynx, and 

 the false vocal cords completely hide them from view when 

 they are approximated. Wyllie points out that an anatomical 

 misconception prevails regarding the nature of the vocal cords> 

 many considering them as the free edges of membranes which 

 are flattened above and below. They are, however, really 

 wedge-shaped projections from the sides of the larynx, the apex 

 of the wedge being directed downwards and attached to the 

 laryngeal wall, its upper flat surface forming the floor of the 

 ventricle of Morgagni, and its projecting edge forming the true 

 vocal cord. 



Their shape is as badly adapted as we can possibly imagine 

 for retaining air in the thorax, though very well adapted for 

 preventing air from entering it. Wyllie's experiments showed 

 that by no adjustment could the true vocal cords completely 

 prevent the exit of air, but that when they were simply 

 approximated, not even being pressed together, they completely 

 prevented its entrance. With the false vocal cords the case 

 was just the reverse ; they present no obstacle whatever to the 

 entrance of air, but when they are approximated they com- 

 pletely obstruct its exit from the lungs, and the air getting 

 behind them into the ventricles of Morgagni, inflates them, and 

 thus the greater the pressure behind them is, the more perfect is 

 their apposition. 



Our own investigations completely confirm those of Dr. Wyllie. 

 He extends his experiments to the production of voice, we have 

 restricted ourselves to the simple mechanism of the closure of 

 the larynx during effort ; but instead of confining our observa- 

 tions to the human larynx, we have made comparative observa- 

 tions on the larynges of some animals. 



Before entering into those in detail, it may be advisable to 

 say a few words regarding the comparative anatomy of the 

 larynx. 



A good anatomical classification of laryngeal variations is the 

 following, proposed by Milne-Edwards* : — 



* Milne-Edwards, Legons sur la Fhysiologie et Vanaiomte comparee de 

 Vhomme et des Animau^, 



2 s 2 



