640 THE VALVULAR ACTION OF THE LARYNX. 



The ventricular bands alone afforded a resistance of 30*0 mm. 

 when gentle lateral pressure was employed. Whilst blowing 

 air from below, a slight telescoping, by pressing the base of the 

 tongue and the epiglottis backwards, being permitted, a bulging 

 upwards of the hyoid fossa and the root of the ventricle under- 

 neath the attachment of the ventricular bands could be dis- 

 tinctly seen. When firm lateral pressure was associated with 

 this movement a much higher pressure was resisted. The 

 ventricular bands alone, when not forcibly held together, pre- 

 sented no resistance whatever to inspiration — in fact, they 

 separated even when the true cords were in contact, and resist 

 ing a powerful suction. 



The true cords alone resist the ingress of air quite as much 

 as when the ventricular bands also are approximated. The 

 resistance is very great, and sometimes reaches 140 mm. of 

 mercury, and even more — in fact, suction of greater power than 

 we could employ failed to separate them, but rather tended to 

 increase their resistance. 



Closure of the glottis is so important a factor in the act of 

 vomiting, that we must now consider how far the development 

 of the false vocal cords in difterent classes of animals is asso- 

 ciated with the easy and perfect performance of the act. 



We find that in Ruminants generally true vomiting is either 

 difficult or impossible. The same is the case with the Solipedes 

 and the Bodentia, while in the cat and dog it is performed most 

 effectually. There is no doubt, in the act of vomiting, another 

 factor than that of simple increase in intra-thoracic, or, more 

 accurately, intra-tracheal pressure, for however greatly this 

 pressure be increased, as in coughing, defecation, or parturition, 

 vomiting does not occur unless the cardiac extremity of the 

 oesophagus be dilated. One explanation of the difficulty with 

 which vomiting occurs in horses, for example, is that the 

 oesophagus passes a considerable way below the pillars of the 

 diaphragm, and that thus the fibres which radiate from it on to 

 the stomach tend to exert rather a longitudinal than a lateral 

 action, and to pull the oesophagus down, or the stomach up, 

 rather than to dilate the orifice. This explanation may, to a 

 considerable extent, be correct, but we think that the other 



