286 Mr. Axvre’s Defeription of the 
through the lower jaw among the pofterior teeth, and fixed 
almoft immoveably. How this happened muft be obvious to 
-every one. (See the figure, tab. XII.) 
“Before I proceed, it will be neceflary' to obferve, firft, iat 
the pofterior teeth of cartilaginous fifhes are always found. ina 
foft, membranous ftate, and but imperfectly formed ; notwith- 
ftanding this, they have the whitenéfs of teeth from a {mall 
quantity of calcareous earth already depofited within their fub- 
ftance. Their hardnefs and perfe& form is acquired as they 
advance ‘towards the anterior parts of the jaws. Secondly, 
that ofthe three ‘angles ‘in each tooth of the fhark, one is 
placed towards the ane another towards the left, and the 
other, which is in thie middle, and the moft acute angle, is 
dire&ed inwardly towards the ‘tongue or fauces. They: are 
placed then in fuch a matiner as that the angles of the teeth on 
the left-fide in one row, approach’the angles of ‘the teeth on the 
right-fide in the next row. Thefe teeth which ftand on a line 
from without inwards, I-call a row ; not thofe which are placed 
‘nearly in a’ parallel line from one fide of the mouth’ to the 
other. 
The fharp:bone of the fting-ray was fixed | in ttle lower jaw 
between two rows of teeth, and at their pofterior part, where 
the firft rudimetits of the future teeth are formed, and it will 
be clear to every one, particularly thofe who are converfant in 
{uch matters, that this could not have happened without pro- 
ducing a great deal of pain, {welling, and diforder in the. part 
where it was fixed. It is unneceflary to enumerate the dif> 
ferent kinds‘ of ‘nvifchief this might occafion. Let it fuffice to” 
‘obfervé, ‘that on account of the fpace taken up by this extra= 
neous body, the teeth on each fide of it, for want of room, could 
never after be perfetly formed. .The teeth on the left- -fide 
A | wanting 





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