J 236 



This i-isino- of the piessnre in the mouth-cavity presses the bottom 

 of the iiioiitli down {K 1 — -2); this displacement is consequently 

 only passive. 



2. F'roni the moment 2 the bottom of the month rises; at the 

 same time (from 2 to 3) the l)ncco-pharyngeal pressure {B), which 

 had remained for an instant stationary, rises to about 3 centimeters 

 of water. The pressure in the lungs presents an equal rising: it 

 appears consequently that the glottis is still open. The period 2 — 3 

 corresponds consequently to the inspiration of the lungs. 



The comparison of the three curves indicates that this phenomenon 

 is to be attributed to an active contraction of the muscles of the 

 mouth-bottom. For the rest the pressure-curve has adiphasical course, 

 which is not shown by the curve of the displacement of the fore- 

 end of the hyoid : this difference indicates that the compression of 

 the air is the consequence of a more complicated movement than 

 that of the registered point. For the rising of the mouth-bottom 

 takes place in two stages and the hyoid moves during its displa- 

 cements up and down. 



3. In the position 3 the bucco-pharyngeal pressure {B) suddenly 

 descends to 0; consequently the opening of the nostrils takes 

 place there. 



Sometimes we perceive in this position an inflexion ; the origin 

 of this inflexion-point can be explained in the following manner: 

 the air in the mouth which was more and more compressed during 

 the former period, offered to the contraction of the muscle an in- 

 creasing opposition, which at the opening of the cavity suddenly 

 ceases; thereupon the upward movement continues with a greater 

 velocity. This inflexion, as can easily be understood, occurs expe- 

 cially in such cases in which the contraction of the muscles is not 

 very strong. 



This last part of the upward movement of the mouth-cavity 

 (beyond ordinate 3) is accompanied by a slight rising of the pres- 

 sure in the bucco-pharyngeal cavity, which follows immediately 

 after the descent of the lever {K); this is in this case a very short 

 expiration-phase in the bucco-pharyngeal ventilation {Vb). 



From this moment 3 the lung-curve proves to be independent 

 of the pressure in the mouth-cavity : consequently the glottis has 

 closed itself at the very moment that the nostrils opened themselves. 



4. The following part of the diagram K, between 3 and 1 

 reproduces the course of the bucco-pharyngeal ventilation. It consists 

 here of three parts: a first descending part of much longer duration 

 than the rising 2 — 3; an upward movement, the top of which is 



