VOL. XXVII.] PHILOSOPHICAL TRANSACTIONS. 5/7 



tympani, in circumference 2^ inches : after which is to be seen the cavitas 

 tympani, consisting of two parts ; the first is 4- inch deep, straight down from 

 the foresaid crena, endued with a great many cellules, distinguished from each 

 other by several osseous solid laminae, irregularly disposed. These excavations 

 were about two or three lines, or 4-, or 4- inch deep. The next cavity is of a 

 surface more smooth, arises much higher than the former, and runs toward the 

 outer table, having several semicircular lines running across. The first cavity is 

 from the right to the left I4- inch, and from front to back I-i- inch. The second 

 cavity I inch in length, and -i- inch at its broadest part. The ossicles, viz. the 

 malleolus, incus, stapes, are of a proportional size, running from the malleolus, 

 which touches the membrana tympani, to the basis of the stapes, which shuts 

 the foramen ovale. It has but a small cochlea in proportion. I searched for 

 the labyrinth, or lineae semilunares, but could find none ; by which I con- 

 cluded, that these caverns in the bottom of the cavitas tympani served for the 

 same uses in this animal, as the meanders of the labyrinth do in others ; and 

 that this second cavity served for receiving and continuing the undulations of 

 the air, for the longer retaining of the sound, as we see the cavous apophysis 

 mastoides does in sheep, cats, dogs, &c. and the spongious one in men. The 

 foramen ovale is but small, and the base of the stapes very thin and slender. 



From the head we go to the trunk, which consists of the spine, ribs, and 

 sternum. The spine is divided into the vertebrae of the neck, back, loins, os 

 sacrum, and tail. The vertebras of the neck differing from each other in several 

 things material, I shall speak of them separately : the first called atlas, has four 

 considerable cavities ; two at the fore part, by which it receives the condyles of 

 the skull, and two at the back part, by which it receives the base of the follow- 

 ing vertebra ; the first two are 24- inches from above to below, and 2 inches 

 from the right to the left. It has a large hole in the middle, divided into its 

 larger part, 3 inches diameter, which is for receiving the spinal marrow, and 

 lesser, which receives the tooth of the following four perforations, or two pair 

 of holes at the sides ; one at its lower and fore part, which receives the arteria 

 cervicalis, or vertebralis from the side of the spinal marrow, and conveys it to a 

 crena, along which it runs, till it again penetrates the same bone, and goes out 

 at the back part ; after which in its progress it perforates all the transverse pro- 

 cesses of the rest of the vertebrae of the neck, as usual in other animals. This 

 crena is guarded on its outside, or at the extremity of the transverse processes 

 by a protuberance, which runs toward the skull 1-i- inch, till it be equal to the 

 sides of the hole for the spinal marrow. At its upper and fore part it inclines 

 obliquely, where it is 3 inches thick, and at its lower and back part it has a pro- 

 tuberance, which is extended where it embraces the tooth. This vertebra is in 



VOL. V. 4 E 



