164 Inez Whipple Wilder. 



To summarize, among the lower urodelcs Proteus and Amphiuma 

 alone possess the homologues of external nasal glands, while the occur- 

 rence of nasal constrictor and dilatator muscles is limited to Crypto- 

 branchus and Amphiuma. 



IV. The Function of the Lateral Gland. 



Because of the apiDarentlj constant anatomical and develop- 

 mental association of the external nasal glands with the constrictor 

 and dilatator muscles of the naris in the salamandrids, Bruner drew 

 the logical conclusion that there is also an intimate physiological 

 relationship between these structures. Following out this line of 

 reasoning, he concluded that, as the function of the muscles is 

 to alternately close and open the external nares during the act of 

 pulmonary respiration, the glands, the orifices of which are upon the 

 margin of the nares, probably sen^e the function of lubricating the 

 edges of the crescentic fold to insure tight closure ; and he suggested, 

 further, the probability that the mechanical device by means of 

 which the secretion is discharged is the pressure exerted upon the 

 gland tubules by the contractions of the constrictor muscle which 

 closes the naris. 



With regard to the embarrassment to this theory presented by the 

 lungless salamandrids, in which the entire apparatus, both glands 

 and muscles, is found, although, of course, there is no pulmonary 

 respiration, Bruner suggested that the function of closing and opening 

 the nares must here subserve some other purpose, such as, for exam- 

 ple, the exclusion of foreign substances, particularly water, from the 

 nasal passages. He thought the muscles in these forms less strongly 

 developed than in the lunged forms, and apparently did not recognize 

 the extreme degree of development which the glands have attained 

 in the lungless species. 



My own recent studies of the breathing habits of both lunged and 

 lungless salamandrids (Wliipple, '06) have led me to believe that the 

 function of excluding water and other foreign substances from the 

 nasal passages is the more generalized and therefore the primpry 

 function of the nasal muscular apparatus. The muscles are on the 

 whole about equally well developed in both lunged and lungless 



