IN THE GENUS SQUALUS. 
149 
the section would be of an oval figure, with the apex point- 
ing inwards. 
Among a considerable number of preparations now before 
me, is one of an elephant (the animal has apparently been 
of great age), where the caliber of the canals, and of one in 
particular, is extremely oblong. 
When dissecting the organ of hearing in various animals, 
as well as in the human subject, I have found the caliber 
of the canals in children, young animals, and birds, to be 
circular, and, in the adult ear, one or more of the semi- 
circular canals slightly flattened, and this oblong form of 
the caliber increased considerably in aged persons, in whom 
it is seldom wanting. The apex in these cases invariably 
pointed towards the vestibule. Indeed this position seems 
to be general, whenever the form of the caliber approaches 
towards an oval. 
Seeing, then, that the caliber of these canals is uniformly 
circular in the young, of whatever class or species, — and 
that, in the adult, one or more of the canals are generally 
more or less of an oblong figure, according to the age of 
the subject, — and that this elongation of the parietesof the 
canals does not diminish the original diameter, and also, 
that the caliber of the membranous semicircular canals in 
the old, as well as in the young, is circular, and always 
continues so when in a healthy state, notwithstanding any 
alteration which may take place in the form of the caliber 
of the osseous or cartilaginous canals ; may it not be in- 
ferred from these circumstances, that the oblong figure of 
the cahber is caused by the vibratory action of the mem- 
branous tubes exciting absorption of part of the cartilagi- 
nous or osseous parietes of the canals in which they are in- 
closed ; and that by the continuance of this excitement the 
oval form of the caliber is gradually increased ? 
This view of the subject will receive additional confirma- 
