1820.] Itoyal Society. 373 



diminished nervous action ; that m.iscular spasm cannot exist 

 where the temperatm'e is steadily above 90°, and that animal heat 

 is produced principally by the action of the brain and nerves. 

 Nitrate of silver, accorduig to the author, applied to the head or 

 spine, elevates the tein[)eratuie, subdues spasm, and restores 

 strength in certain parah tical cases ; and applied to enlarged 

 joints, produces a more rapid absorption than any other remedy. 



The iSociety adjourned tiil after Easter. 



April 13. — The Society resumed its meetings, and a paper, by 

 Sir E. Home, was read on the Milk Teeth, and Organs of riear- 

 ing of the Dugong. The skull from which the following descrip- 

 tion was taken, and which is the only perfect one in Europe, 

 was sent from Sumatra by Sir Stamford Raffles. The milk tusks 

 of this animal resemble those of the narwhale and elephant, 

 being, like them, deBcient in external smoothness, when conii 

 pared with the permanent tusks. But they are peculiar in havin 

 a shallow cup attached to their base, apparently for the purpose 

 of receiving the point of the permanent tusks as soon as formed, 

 and for directing them forward in the same course as that of the 

 milk tusks, and which is different from that in which the perma- 

 nent tusks were originally directed. The milk tusks of the 

 dugong have hitherto been mistaken for its permanent tusks ; 

 but as no full grown individual has been yet examined, the 

 form, &c. of the permanent tusks are unknown. 



The grinding teeth of this animal differ from those of all others. 

 They consist of a double cone, the external crust of which is not 

 enamel. This crust covers an internal harder coat, and the bulk 

 of the tooth consists of soft ivory ; hence in wearing down, they 

 will assume a concave form. 



The organs of hearing also in this animal are quite peculiar. 

 The malleus and incus are fastened to the sides of the tympanum 

 by a bony substance extending across the intervening space. 

 The stapes is opposed to, but not connected with, the foramen 

 ovale, nor isitanchylosed with the ramus of the incus. The handle 

 of the malleus projects in the centre of the circle over which the 

 membranum lympani had been spread ; and hence, in the recent 

 animal, is probably attached to the centre of that membrane 

 As the habits of the dugong resemble those of the hippopotamus. 

 Sir Everard was induced to examine the organs of hearing in the 

 latter animal to see if they were similar to those of the dugong. 

 He found them, however, very different, the ossicula auditus 

 being detached from the skull, and readily dropping out at the 

 external orifice. In the dugong, the semicircular canals and 

 cochlea are very small. Sir Everard was induced to conclude 

 from the above remarkable construction of the organs of hearing, 

 that this animal, perhaps more than any other, hears by means 

 of vibrations conveyed through the bones of the skull to the 

 ca^nals and cochlea. 



