314 



INEZ WHIPPLE WILDER. 



and closing the naris develops. This consists of a constrictor 

 and a dilatator muscle (men and mdn) and forms an effective 

 apparatus very characteristic of adult amphibians (Bruner, '96 

 and '01, I. W. Wilder, '09). 



The naso-labial glands have to do with the terrestrial life into 

 which the process of metamorphosis introduces the animal, in that 

 they not only keep pliable the thin crescentic fold which by means 

 of the contraction of the constrictor muscle closes the external 

 naris against the entrance of foreign bodies, such as dirt when the 

 animal is burrowing, but they also appear to have the peculiar 



int nip 



men 



FIG. 19. Horizontal section through head of adult Desmognathus fusca, X 20. 

 Ac, acinous glands of skin; gr, cross-section of naso-labial groove; int, intermaxillary 

 glands; men, M. constrictor naris; nc, nasal capsule; nl, naso-labial glands; nli, nit, nh, 

 the first, second and third naso-labial glands respectively; nip, tubules of naso- 

 labial glands within the premaxillary foramina; ns, external naris; 61, olfactory 

 nerve; op, internal nasal branch of ophthalmic nerve. 



function of so repelling water from the surface of the skin immedi- 

 ately surrounding the naris and bordering the naso-labial groove 

 that the latter may, by capillary action, almost instantaneously 

 drain off the tiny drop which fills the nasal depression after a 

 temporary immersion in water. Thus this water is prevented 

 from entering the nasal passage when the animal, upon emerging 

 from the water, reopens the nares by withdrawal of the crescentic 

 fold. The nasal passages are by this means kept dry and fully 



