The Lateral Nasal Glands of Amphiiima. 165 



forms. Moreover, the contact of any foreign body with the snont is 

 followed at once by the closure of the nares. As a general means for 

 protecting the delicate nasal epithelium from dirt and other foreign 

 matter in forms such as Desmognathus and Plethodon, which are 

 burrowing in hal)it, this device must be invaluable. Further, in all 

 the luugless forms (Plethodontidse and Desmognathidne) I have 

 found that the exclusion of water from the nasal passages is an abso- 

 lutely fixed habit, so much so that even when they are forced to 

 remain under water for days, the nares are kept closed and aquatic 

 bucco-phar>'ngeal respiration, such as occurs in the lunged forms 

 under similar conditions, is never established. So great is the 

 importance of this exclusion of water from the nasal passages, that 

 in connection with each external naris a highly specialized device, 

 the naso-labial groove, has developed, which acts as a gutter through 

 which the tiny drop of water which naturally lodges in the nasal 

 depression is drained off before the naris opens, and is thus pre- 

 vented from being drawn into the nasal passage. 



Even in the case of the lunged salamandrids a temporary submer- 

 sion is accompanied by closure of the nares, and thus the animal is 

 spared the physical inconvenience incident to a change of respiratory 

 medium, although a prolonged stay in the water involves, in all the 

 lunged species that I have experimented with, a transition from 

 aerial to aquatic bucco-pharyngeal respiration. 



Undoubtedly this device for excluding foreign substances from 

 the nasal cavities has become of use in pulmonary respiration as a 

 means for preventing the escape of air during that phase of the 

 respiratory act when the mouth is used as a pump to force air into 

 the lungs. But that closure of the nares for this purpose is not essen- 

 tial is shown by the fact that jSTecturus, Siren, and Proteus all effect 

 pulmonary respiration in the absence of these muscles, and frequently 

 (in ISTecturus at least) Avith the escape of air through not only the 

 nares, but also the gill slits. Even in Amphiuma, in which the nasal 

 muscles are present, there is frequently some loss of air through the 

 gill slits during the act of filling the lungs. This escape of air can 

 be readily observed in both l^ecturus and Amphiuma when the ani- 

 mals are in the water. In the case of lunged salamandrids, also, I 



