356 Henry L. Bruner 



has devised tlie delicate and complicated adjustments which 

 are employed for closing the mouth and nares during res- 

 piration. It is a peculiar fact that the frog, to whom striated 

 nasal muscles have been denied, has nevertheless found a 

 perfect substitute for such muscles by employing the sub- 

 mentalis and the masticatory muscles for closing the ex- 

 ternal naris. 



In conclusion, the most important contributions of the foregoing 

 pages to the anatomy and physiology of the respiratory mechanism 

 of amphibians may be summed up as follows. 



1) The muscle apparatus which is used for opening and closing 

 the apertura naris externa in the Salamandrina lies in the fenestra 

 rostro-lateralis of the cartilaginous nasal capsule. The individual 

 nasal muscles are attached to the margins of the fenestra rostro- 

 lateralis or to adjacent parts. 



2) The relation of the glandula nasalis externa to the nasal 

 muscles in Triton alpestris, Salamandra maculosa and Amblystoma 

 tigrinum indicates the existence of a functional adaptation, by virtue 

 of which the secretion of the gland is forced out by the nasal 

 muscles at the time of closing the external naris. 



3) The nasal muscles and the glandula nasalis externa of Triton 

 begin their development at about the same time and reach functional 

 maturity a short time before the metamorphosis is completed. 



4) The nasal muscles of the Salamandrina, which are composed 

 of smooth tissue, arise in situ from the mesenchyme. 



5) The intermaxillary apparatus designed for closing the external 

 naris of Eana may be set in motion, a) by the contraction of the 

 musculus submentalis, or b) without the aid of this muscle, by the 

 simple protraction of the lower jaw. 



6) The loss of solidity of the two jaws in Rana has made it 

 impossible to close the mouth securely by simple adduction of the 

 lower jaw. To secure this end special adaptations are required, 

 among which must be counted, a) the form and mode of fitting 

 together of the jaws, b) the development of the upper lip with the 

 musculus labialis superior, and c) the protraction of the lower jaw. 



7) The musculus labialis superior of Rana is a smooth muscle 

 which extends through the upper lip from one angle of the mouth 

 to the other. It maintains a constant tension, and thus aids in 

 preserving a close union of the jaws during inspiration. 



8) Protraction of the lower jaw in Rana has a double signifii- 



