soo Mr. Carlisle on the Physiology of the Stapes > 
detached end forms a rounded enlargement, which is articu- 
lated by a sort of hinge joint to the body of the incus. Three 
muscles are fixed to the malleus, the most powerful of which 
draws the manubrium, and membrana tympani perpendicularly 
inward ; the next in strength is inserted upon a slender 
stem of bone which forms a right angle with the manubrium, 
and on the plane of the membrana tympani. The smallest 
muscle is fixed to the processus major, pulling the malleus 
backward, and pressing its head against the joint of the incus. 
These muscles are all restricted in their actions to the changes 
produceable on the membrana tympani, because the strong 
connections of the joints between the malleus and incus, and 
the incus and stapes, admit of little motion ; indeed the former 
joint is deficient in many animals. The incus has no muscles, 
and forms only a passive intervention between the malleus 
and stapes, which last bone has a peculiar muscle appropriated 
to itself. Hence it appears, that the first series of ossicula 
auclitus has a different office from the stapes, as will be subse- 
quently explained. 
The bone, to be now particularly considered, has been called 
stapes, staffa, stapha, or stapeda, from its resemblance to the 
stirrup of a saddle. It was first observed about the middle of 
the sixteenth century ; and Philip ab Ingrassias, Realdus 
Columbus, and Bartholom^us Eustachius, have contested 
the honour of its discovery. 
The human stapes is of an inch in height, and in 
width at its basis : it weighs, when dried, ~ of a grain. 
It is divided into the following parts, viz. 
The capitulmn, or articulating head, which joins the os 
lenticulare. 
