SUCCESSION OE THE POISON-FANGS OF SNAKES. 
385 
Fig. 2. From a full-grown rattlesnake. 
A section in most respects similar to fig. 1, with the exception that the 
tooth in use ( x ) is not to be replaced so speedily as the corresponding tooth 
in fig. 1. The partition (b) is deflected to one side, there being only one 
tooth free in the pouch. 
Fig. 3. English viper. 
This section is taken from the same specimen as fig. 1, but through a spot 
nearer to the fixed base of the tooth (see Diagram, fig. 12, p. 382). 
At the top of the figure is seen in section the parapet of bone which 
stretches up from the body of the maxillary bone in front of the teeth. 
2 , s, 4. Portions of three successional tooth-germs occupying the remaining 
space between the parapet of the maxillary and the transverse bone. 
Fig. 4. English viper. 
From the same specimen as figs. 1 & 3 ; taken through the attached base 
of the poison-fang ( i ). 
It is to be noticed that there is room for two poison-fangs, side by side, and 
that these two positions are alternately occupied by the working teeth. 
The tooth 2 , which is rapidly becoming attached, will be fixed in place 
by a framework of coarse bone (k), which shoots out from the maxillary bone 
and becomes united with the dentine. 
Fig. 5. Indian cobra. 
Transverse section, immediately behind the poison-fang. 
The successional teeth come to occupy the same spot as their predecessors, 
and are developed, unlike those of viperine snakes, in a single series. 
Compare this figure with that of the successional teeth of a harmless snake 
(Phil. Trans, part i. 1875). 
Fig. 6. Transverse section of a very young tooth-germ from an English viper. 
It does not differ as yet in any particular from the tooth-germ of any other 
Ophidian tooth. 
Fig. 7. Viper. Tooth-germ a little older. 
The groove, to become afterwards a canal, has commenced, but as yet the 
enamel-organ occupying it is not altered from that surrounding the rest of the 
tooth. 
Fig. 8. English viper, at a somewhat later stage. 
Fig. 9. English viper, later stage. 
The enamel-organ occupying the interior canal has become transformed 
into a tissue of stellate cells ( e '). 
Fig. 10. Process of epithelium, / (enamel-germ of Kolliker), from which a yet younger 
enamel-organ will ultimately be formed ; at e , d is seen the youngest tooth- 
germ as yet actually formed. 
3 H 
mdccclxxvi. 
