rENOMOUS SNAKES AND THEIR VICTIMS. 



321 



and then commence the extraordinary swallowing, having often enveloped their prey in the folds of 

 their body, crushing it more or less. 



In the first group a special adaptation of the usual bones of the head enables the contents of the 

 poison-gland probably an altered and adapted salivary gland to be injected, and there are remark- 

 able movements permitted, which enable the Snake to bite and to protect its fangs from subsequent 

 injury. Then in the act of swallowing, a peculiar mobility and separability of the jaws and associated 

 bones come into play, and this is, of course, noticed also in the second group. In endeavouring to explain 



YELLOW VIPER, OR FER DE LANCE. 



these necessary actions and movements it must be noticed, first of all, that whilst the bones which 

 enclose the brain of the Snake are solidly united, those of the face, upper and lower jaws, and palate, 

 and those which joint the lower jaw with the skull the lower jaw with the quadrate, and this with 

 the squamosal are loose and more or less inter-connected by fibrous tissue, permitting of much separa- 

 tion and movement (see Note, p. 275). The movements and special adaptations are of two kinds, 

 those relating to the striking with the poison fang, and those which refer to the forcing back 

 the prey into the mouth and the expansion of the jaws sideways, in order that a huge morsel 

 should pass into a dilatable throat. The first will be now explained, and the last will be noticed 

 farther on. 



The Rattlesnakes have been carefully studied, and they may be taken as the type of the veno- 

 mous Snakes, so far as the construction of the skull is concerned. 



