362 SNAKES. 



found no trace of fangs in young vipers which he examined 

 with a lens ; but these had not yet been born. The possible 

 cause of functional development in this little viper's fangs 

 may be found in chap. xxiv. of this work. 



Another erroneous impression regarding fangs has been 

 produced by confusing those that are ' fixed ' and those that 

 are 'moveable.' All truly are fixed firmly into the jaw; but in 

 the viperine snakes the very short bone itself is moveable by 

 a volitionary action, so that it partially ' rotates,' and with it 

 the fang. The Elapidce have fixed or * permanently erect * 

 fangs, and when the mouth is closed these fit into a depression 

 in the lower jaw. Viperine fangs only can be erected or 

 depressed at pleasure. It is those which spring into place 

 for use like a pen-knife half opened, and which when at rest 

 are folded back, like the knife shut up again. This action has 

 been most lucidly described by Coues in connection with the 

 Ci'otalidce, under which head I will quote from his paper. 

 Schlegel himself is not very clear in his distinctions between 

 those serpents that have ' moveable ' fangs and those which 

 have not, but Cuvier had already described them as crochets 

 mobiles. Indeed, it is since the date of Schlegel's work that 

 more complete investigations have revealed closer anatomical 

 distinctions. We therefore find in some of our highest-class 

 encyclopedias, if not of recent date, mis-statements regarding 

 fangs which unfortunately have been quoted in many works. 

 'Venomous serpents depress their fangs,' says Schlegel's 

 translator, true to the text, but as if it were common to all. 

 Describing deglutition, Schlegel says * the same in all ' ' sans 

 en exccptcr les veniineuXy qui lors de cet acte redressent leur 

 crochets et les cachcnt dans la gaine des gencives, pour ne poijit 



