VOL LXXXIX.] PHILOSOPHICAL TRANSACTIONS. «>25 



in extent to that of 1 of the processes contained in the large tooth of the full- 

 grown animal: the second has a grinding surface equal to that of 2 such processes: 

 the 3d is still larger, its surface being equal to that of 3 processes. These 3 teeth, 

 in their general appearances, resemble those of the common hog; they have also 

 the same kind of fangs; their only peculiarity is, the enamel being intermixed with 

 the substance of the tooth, but without any bony matter surrounding it. The 4th 

 or last tooth is very different from the others, and exactly resembles that found in 

 the large head, only that this is in a growing state. It is composed of 7 processes, 

 united together; these are in different stages of growth, fitting them to come for- 

 ward in succession, similar to those of the elephant. The 2 first have their grind- 

 ing surface worn smooth: the points of the next 2 have recently cut the gum; 

 and the other 3 are still concealed in the jaw, not being completely formed; of the 

 last of these the first rudiments only are to be seen. This large tooth, which may 

 be considered to be a 2d set of teeth, as the concealed processes enlarge, advances 

 forwards, pushing the other teeth before it: the most anterior of these, as soon as 

 its body is worn away, has its fangs removed by absorption, and drops out : the 

 same thing takes place with the 2d and 3d; and in this way room is made for the 

 large 1 to supply the place of all the others. 



These peculiarities in the teeth of the Sus iEthiopicus, led to the examination 

 of the teeth of the other species of the same genus, all of which appear to resemble 

 the human grinders, only that the last in the jaw has a broader grinding surface 

 than the rest, which is common to most quadrupeds. It is worthy of remark 

 that the number in each side of th.e jaw in the common hog is 7 ; in the Pecary, 

 6; in the Babyroussa, 5; and in the Sus ^Ethiopicus, till a certain age, 4. It is 

 curious, that one species of a genus should differ so widely from all the others, in 

 respect to its teeth ; and should be allied to the elephant in the structure of its 

 tusks, the mode of formation of the grinding teeth, and the manner in which 

 they succeed each other. From these circumstances it appears that the Sus ^Ethio- 

 picus, in a natural state, is supplied with a different kind of food from that of 

 other hogs, and is an animal of greater longevity. 



On comparing the internal structure of the elephant's tooth with that of the 

 horse, cow, and sheep, it was found, that they were similar, in having an inter- 

 mixture of bone with the substance of the tooth, but that they differed materially 

 from each other in the proportions and situations of the bony portions. Each of 

 these animals having the grinding surface of their teeth adapted for particular kinds 

 of food, the parts composing that surface are variously combined, so as to answer 

 the purpose for which the teeth are intended. In all of them, the mode of growth 

 is the same; the substance of the tooth is first formed, and the bony part is after- 

 wards adapted to the irregularities of that surface. In the horse's grinding teeth 

 the processes are 2 in number; and, in an early stage of their growth, they appear, 

 as well as those of the elephant, to be separate teeth ; they differ however extremely 



