The Smooth Facial Muscles of Anura and Salamandrina. 347 



time with the closing of the external naris, or simpl}^ maintain a 

 uniform tension, must be answered in favor of the latter view. A 

 movement behind the naris at the time of inspiration, indeed, suggests 

 rhythmic contraction the nasal muscles, but this movement wholly 

 disappears if the mouth is held open, although movements of in- 

 spiration (bucco-pharyngeal movements) still occur as usual. Since 

 then we have no reason to believe that the contraction of 

 the nasal muscles is modified by the opening of the mouth, 

 we must conclude that such contraction does not produce 

 marked movements at all but tends to maintain a steady 

 tension of the parts to which they are attached. 



To account for the movements which occur behind the external 

 naris two possibilities present themselves. Such movements might 

 perhaps be caused a) by the impact of the cartilago alaris against the 

 plica obliqua, or b) by the action of the compressed air within the nasal 

 cavity upon the soft nasal walls. The inadequacy of the impact of the 

 cartilago alaris as a cause of the movements is clearly shown, however, 

 if a suitable object be placed between the tips of the jaws, so that 

 the nares may be closed, while the jaws are still seperated behind 

 the rostrum. Under these conditions no movements occur behind the 

 naris; as soon, however, as the opening between the jaws is closed, 

 so that the air can not escape from the mouth the movements 

 reappear. We may conclude then that the movement which 

 occurs behind the external naris of Rana at the moment of 

 inspiration is due to the pressure of the air confined within 

 the mouth. For such a movement the anatomical conditions of the 

 region are entirely favorable, for the nasal wall has a very incom- 

 plete solid support behind the external naris, a large area between 

 the nasale and the facial portion of the maxillare being wholly 

 without skeletal parts. The movements behind the external naris of 

 Rana are to be explained in the same manner, therefore, as certain 

 movements of the eye and tympanic membrane, both of which, as 

 is well known, are forced outward during inspiration by the com- 

 pressed air within the bucco-pharyux. 



The opening of the external nares of Rana, as already described 

 by Gaupp (20), is to be attributed under ordinary circumstances to 

 the elasticity of certain parts, including especially the processus 

 praenasales inferiores and the various syndesmoses of the inter- 

 maxillary apparatus. The importance of the processus praenasales 

 inferiores is clearly indicated by their relation to the intermaxillaria, 



Morpholog. JaLrbucli. 2U. 2-1 



