NASO-LABIAL GROOVE OF LUNGLESS SALAMANDERS. 25 



CONCLUSIONS. 



1. The naso-labial groove is a characteristic of the adult stage 

 of the Plethodontidce and Desmognathidce. 



2. Associated with the naso-labial groove is a system of 

 glands which lie beneath the skin, and, in the main, external to 

 all skeletal structures and open upon the border of the naris and 

 groove. 



3. These glands are homologous with the external nasal glands 

 of other Salamandrida and of the Am/nt, but in the lungless 

 families certain of them attain an enormous development. 



4. The function of the naso-labial apparatus is to quickly 

 remove from the nasal depression the small quantity of water 

 which collects there when the head has been flooded with 

 water. The object of this prompt removal of water is to permit 

 an immediate resumption of aerial bucco-pharyngeal respiration 

 after its temporary interruption by immersion in water. 



5. The function of the glands is -to guard both the naris and 

 the groove against a continual overflow of water from the neigh- 

 boring wet surface of the skin. The secretion is of a nature to 

 repel water and by its agency water lodged in the nasal depres- 

 sion is cut off from that on the surrounding surface and can 

 therefore be removed through the groove. 



6. The groove performs its function partly through its capil- 

 lary action, thus overcoming the surface tension when the quan- 

 tity of water to be removed is very small ; and partly merely as 

 a gutter permitting the flow of the fluid from the naris to the lip. 

 In its function it is assisted by the motion of the crescentic fold 

 of skin which is drawn across the naris to close it against the 

 entrance of water. The withdrawal of this fold tends to push 

 the water out of the depression into the groove. 



SMITH COLLEGE, NORTHAMPTON, MASS., 

 February 27, 1906. 



BIBLIOGRAPHY. 

 Born, G. 



'77 Uber die NasenhShlen und den Thranennasengang der Amphibien. Morph. 

 Jahrb., Bd. II. 



Bruner, H. I. 



'96 Ein neuer Muskelapparat zum Schliessen und Offnen der Nasenlocher bei den 

 Salamandriden. Arcliiv fur Anat. und Phys. Anat. Abth. 



