36(5 PHILOSOPHICAL TRANSACTIONS. [anNO I/O/. 



The bony cavity of the ear is covered at each end by a membrane; the for- 

 mer is called the membrane of the drum, and the other is directly opposite to 

 it; the exterior one is stronger than the interior. They are connected together 

 by the handle of the malleus adhering to the external membrane, and the upper 

 part of the stirrup to the internal, which, by the intervention of the incus and 

 the orbicular bone, form a chain, and they seem to be acted on, and to react 

 by these small bones reciprocally. 



Whether artists had any respect to this original, when they first devised 

 drums, I cannot sav; but nothing can more nearly represent the natural than 

 the artificial does ; the skins of this answering to the membranes of that, the 

 wooden cylinder to the bony cavity; the sound of the drum would be iiat. 

 without a hole in the side, and nature has given a passage from the palate to 

 the ear. The skins of the drum would lessen the sound, if they were not 

 kept on the stretch ; so would those of the other flag, if the handle of the 

 hammer and the stirrup did not keep them tense. 



This inner membrane is closely stretched before the labyrinth, the foramen 

 rotundum, and the passage into the cochlea, that so the sound may be the more 

 augmented on its approach to the nerves. The stirrup is generally broken in 

 dissecting the ear, particularly that cover which goes over the bone on each 

 side; but if it be carefully opened, the stirrup is entirely covered with a mem- 

 brane, which forms a cavity flatly oval, and the inside excavated. 



Microscopical Observations of the salts of Pearls, Oyster-shells, ^c. By M. 



Leuwenhoeck. N°3n, p. 241 6. 



Pearls are prescribed as a very wholesome medicine on divers occasions, to all 

 those that are able to pay for them.* Now in order to try their supposed virtues, 

 I took seven small ones, all which being laid in a row together, did not exceed 

 the length of an inch. I put them on a strong charcoal fire, and made them 

 red-hot; after which throwing them into clean rain water, they immediately 

 burst in pieces; on which I took the pearls and put them into a glass tube, 

 and placed the tube and pearls over a sharp fire, till they were both red-hot. 

 On the bursting of the pearls there arose a smoke, and there was also a yellow- 

 ish oil drawn from them. Those oily particles adhered to the sides of the glass 

 in divers places, and were divided into such exceedingly small globules, that 

 several thousands of them together did not equal a single grain of sand; but 

 in other places the particles of oil were coagulated into much larger figures. 



When the glass tube where the pearls lay began to melt, I threw those pieces 



* Such an expense need never be incurred^ crabs>claws or common oyster-shells being just as 

 good for medicinal purposes. 



