260 Mr. C. S. Tomes on the [Feb. 3, 



But in all the viperine poisonous snakes which I have examined a 

 strikingly different arrangement is displayed. Upon the movable maxil- 

 lary bone there is room for two poison-fangs, side by side ; and in a 

 macerated skull the tooth in use occupies an extreme position, sometimes 

 on one side, sometimes on the other. In sections displaying all the soft 

 part in situ, the remaining space is generally occupied by a tooth which is 

 in process of becoming attached; and, in whatever part of the area of tooth- 

 development the section be taken, the successional teeth are arranged in 

 pairs, in two parallel series. Thus there will be a right-hand series, con- 

 sisting of the tooth in place and of four successors, and a left-hand series, 

 consisting of the tooth next about to be in place and four successors. 



When a tooth of the right-hand series has finished its period of work 

 and is about to be shed, it is succeeded by a tooth of the left-hand series, 

 which comes up by its side, and vice versa. A septum of connective 

 tissue separates the two parallel series, and is continued out into the 

 pouch, which conceals the poison-fangs when at rest, as a free hanging 

 fold : its use appears to be to keep the long axis of the tooth in the right 

 direction prior to its becoming firmly attached, and to prevent a right- 

 hand tooth from getting into the place of one of the left-hand series, and 

 vice versa. 



It is obvious that this manner of succession is well adapted to avoid 

 loss of time in the changing of the poison-fangs, for much can be done 

 towards the fixation of a new tooth before the old one is detached. That 

 the succession is both rapid and regular would appear to be indicated by 

 the fact that the successional tooth-sacs are very numerous (often as many 

 as ten), and that they are arranged in pairs, the two being almost abso- 

 lutely alike in size and stage of development. Now as any given tooth 

 of the one series is succeeded or preceded by its fellow in the other 

 series, one might expect, if any great interval of time were to elapse, that 

 the one would be materially more advanced than the other. "When such 

 is not the case, one is led to the inference that the succession is rapid and 

 also regular. 



In the cobra, the new tooth has to come into place and become attached 

 after the loss of the old one ; and this, it may be inferred, would take 

 much more time. May this not be the explanation of the feat performed 

 by Indian jugglers with the cobra, and their selection of this snake for 

 such purposes ? A cobra disarmed would remain harmless for some 

 considerable period ; a rattlesnake similarly treated would be furnished 

 with a new weapon very speedily. 



I have examined specimens in spirit of a few other colubrine snakes ; 

 and although such examination is less satisfactory than the methods 

 which may be pursued with fresh specimens, I believe it will be found to 

 hold good that in those snakes which have a movable maxilla carrying 

 but one tooth, the successional teeth are developed in two parallel series, 

 this being the highest specialization of the poison-apparatus. 



