11 



mobile and, -when pushed forward by the ectopterygoid, the 

 fang usually lying supine becomes perfectly erect, the angle 

 moved through being little short of 90°. (The Vijperina). 



These stages of development are far from being abrupt ; 

 . when the fauna of Australia is taken into consideration, 

 we find steps between them, both as regards development 

 of maxillary and fangs, and degree of venomous quality. 



The poison apparatus is best studied in the large and 

 well developed examples afforded by the cobra and the 

 chain-viper. On examining the mouth of the cobra, dis- 

 sections of which are given in Plate III, the peculiarities to 

 be remarked are — the gingival envelope of the fang, the 

 depression in the lower lip for the reception of the fang 

 when the mouth is shut, and the absence of any teeth 

 (except a rudimentary one) behind the fang. Slit up this 

 gingival fold and the fang will then be exposed ; it will be 

 seen to be fixed in very much the same position as a dog's 

 fang, though curving more backwards, and to fit into a 

 depression in the lower lip. Now dissect the skin off the 

 cheek of the cobra, from the nostril in front to the angle 

 of the mouth behind. A large flask-shaped gland will be 

 exposed on the cheek, extending for half an inch or more 

 behind the eye ; it is continued by a duct along the lower 

 edge of the orbit as far forwards as the nostril ; a dense 

 fibrous sheath covers the gland and formS' a point of attach- 

 ment to fibres of the temporal muscles. Cut through the 

 duct at its beginning, just behind the eye, and a canal of 

 very small calibre will be seen in its axis; pass a fine 

 bristle dovm .the canal, and by careful manipulation this 

 probe will be seen to go to the end of the maxilla, turn down- 

 wards over it, and enter the mouth inside the gingival 

 envelope of the fang, and in front of an orifice in the base 

 of the fang. This examination requires careful dissecting 



