the poisonous Fangs of Serpents. 459 
rounded, though in very close contact, they do not cohere. In 
the viper, the slit seems filled up by the enamel, which being 
nearly transparent, a bristle in the poison tube may be seen 
through it, and causes an appearance as if the slit was open. 
In the first case, therefore, there is no channel observable on 
the exterior of the tooth; the line of junction, however, of the 
edges of the slit is very distinctly marked: in the cobra de ca- 
pello there is an external furrow from the foramen of the base to 
that of the apex, owing to the edges of the slit being rounded ; 
the same is the case in those species of Aydrus that 1 have ex- 
amined. 
T should observe, that the poison tube is not coated with ena- 
mel; for the membrane or capsule in which the tooth is formed, 
and from the inner surface of which it is well known that the 
enamel is deposited, does not pass between the edges of the slit 
into the poison tube: as, however, it passes over the slit, it will 
cover it with enamel, and in some cases, by that meaus alone, the 
edges become soldered together. : 
As some excuse for the errors which may be found in this pa- 
per, I must observe, that many of my observations have been 
confined to small teeth of a species of hydrus, which I was there- 
fore obliged to dissect under the microscope. 
I have to thank Sir Everard Home fer the great interest that 
he has taken in the object of my inquiry, and for the assistance 
which he has afforded me; on the value of which it would be 
needless to enlarge before the members of this Society. 
The drawings annexed to the paper will sufficiently attest my - 
obligations to Mr. Clift. I owe much to him, in addition, for the 
zeal with which he exhibited to me every thing in the Museum 
of which he has the custody, that was likely to promote my views, 
and for information upon several points, which was required in 
the progress of the investigation. 
Description of Plate V. 
a, b, c,d, ave representations of the poisonous fangs of the 
cobra de capello, in four stages of their growth. 
A, B, C, D, are magnified representations of the same. 
A, is a full-grown fang firmly fixed to the bone. 
B, is not quite perfect, the lower part of the foramen at the 
base not being yet formed. 
C, in this a very small part of the foramen is formed. 
D, the part of the tooth above the foramen alone appears. 
B, F, G, are end-views of B, C, D, showing the poison tube 
nearly surrounded by the cavity which contains the pulp, and the 
proportions between them, at three different parts of the tooth. 
H, a section made by sawing the full-grown fang A, just oun 
the 
