SUCCESSION OE THE POISON-EANGS OE SNAKES. 
381 
cobra as a snake for snake-charming exhibitions \ A cobra deprived of its poison- 
fangs would remain harmless for some little time, but a rattlesnake similarly disarmed 
would sooner replace its lost weapon. 
The colubrine poisonous snakes are less specialized than those of the viperine type ; 
the maxillary bones are immovable, and are not very short ; they also often carry a few 
other teeth behind the poison-fang. It is interesting to see that this lower degree of 
specialization is found in the processes of development and succession, so that the 
region in which the successional poison-fangs are being formed is strikingly similar to 
that in which the ordinary ophidian teeth are developed, whilst in the viperine snakes 
it is strikingly dissimilar and highly specialized. 
To return to the consideration of the tooth-forming region of the vipers. I have 
shown that the teeth are developed in two parallel series, separated by a connec- 
tive-tissue partition, which is prolonged so as to hang as a free fold ( b in figs. 1 & 2) into 
the pouch occupied by the working tooth, and that the new tooth is taken from the one 
or the other series alternately. The successional teeth are arranged in two straight 
lines in the rattlesnake (fig. 2) and in two curved lines in the viper (fig. 1) ; but at 
another point in the rattlesnake’s head the lower successional teeth are arranged along 
a slight curve, so that this difference is not of any moment. 
The appearances presented by the tooth-forming area differ according as the 
section is taken near to the base or near to the tip of the working tooth. Close to the 
maxillary bone we see either the bases of two teeth, as in fig. 4, or the base of one tooth 
and the vacant space just vacated by another, as would be seen if we had a section at the 
base of the teeth represented in fig. 2. A little further down we have the state of 
things represented in fig. 3 (also from the same viper as figs. 1 & 4), in which the bases 
of four teeth are seen, which may be identified and compared with those in the other 
figures by their numbers, whilst as we approach nearer to the tip of the working tooth 
as many as ten teeth come into view. 
Nearer to the tip of the active tooth we have passed beyond the region where tooth- 
development is most active, so that figs. 1 & 2 may be taken as giving the best idea of 
the parts. In order to make the relations of the several teeth to one another clear, I have 
constructed the diagram fig. 12 (p. 382), which is intended to show the positions of the 
transverse sections which have been figured on Plate 37 ; an actual drawing of a longi- 
tudinal section would not have answered the purpose so well, as the several teeth are so 
close together as to appear confused. 
It now remains to give a short account of the structure and development of the indi- 
vidual teeth, and of the manner in which they become attached. The earliest tooth- 
germ is not distinguishable from that of any other tooth. A band of epithelium, which 
may be seen at / in figs. 1 & 10, grows out into the connective tissue beyond the youngest 
germ ; its extremity becomes converted into an extinguisher-like enamel-organ covering 
over a newly forming dentine pulp. A transverse section of such a young germ is 
shown in fig. 6, and at s and 9 in fig. 2. The dentine pulp is surrounded by a thin 
