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Mr. Carlisle on the Physiology of the Stapes. 
The ossicula auditus in man, and in the mammalia, form a 
series of conductors, through which sounds are transmitted, 
from the membrana tympani, into the sensitive parts of the 
organ. The number, forms, and relative junctions of these 
ossicles are various ; but, in all cases, their office seems limited 
to the conveyance of sounds received through the medium of 
air ; because fishes have no parts corresponding with them. 
In two classes of animals, the aves, and amphibia, of Linnaeus, 
one bone, in the situation of the stapes, is the only ossicle of 
the tympanum : in all other animals it is placed next to the 
seat of sensible impression, and most remote from that part of 
the organ on which sounds first impinge. 
The ossicula auditus are formed of bone, resembling that of 
teeth ; it is close in texture, and brittle : in the growing state, 
composed of a vascular pulp, the ossification of which is com- 
pleted soon after birth ; and, like the teeth, they cease to grow 
after that process is finished. The malleus and incus are 
hollow, and possess an internal periosteum ; and the whole 
series is covered by a reticular membrane which has no red 
blood-vessels in the adult. It has been asserted by many 
authors that fat, or marrow, is contained in these bones, but I 
am induced to attribute their occasional greasy appearance to 
transudation from the neighbouring parts, during the stage of 
putrefactive maceration, seeing that all such bones when taken 
from recent subjects, are free from the marks of fat. Although 
density seems to be a requisite condition, yet it is convenient 
that the bones should not be massive, as their figures and rela- 
tive adaptations evidently show. 
The malleus is united to the membrana tympani throughout 
half its long diameter, by a process called manubrium ; its 
