NUTRITION PROPER. 



299 



tion of mammals, and therefore universally used by 

 naturalists. A number of these are given below: 



Type 



i 3_ 3 

 ' 3—3 



c, 



I 1 



I 1 



pm., 



4^4. 

 4—4' 



m. 



3— 3 -,,, 



7, ~r, — 44" 



3—3 





. 2 — 2 

 ' 2 — 2 



c, 



I 1 



I 1 



pm., 



2 — 2 

 2 — 2' 



m. 



3 — 3 

 3—3 







j 3 

 3 



c, 



I 

 I 



pm., 



4 . 



4 ' 



m. 



-f = - 





j 3 

 3 



c, 



I 

 I 



pm., 



3 

 2 



m. 



1 

 —=30. 







 3 



c, 



O 

 I 



pm. 



3 

 3 



m. 



-f=3, 





2 

 1 



c. 



O 

 O 



pm. 



3 

 2 



m. 



^-=28. 

 3 







 



u. 



I 

 I 







m. 



, 4 -18. 







3 







 



t. 



O 

 







 































To explain : In the type mammal, probably in all the 

 early Tertiary mammals and in the most generalized 

 mammals, like the hog now (Fig. 183), there are forty- 

 four teeth in all, of which twelve are incisors — i. e., three 



each side above and below, i. = 



'•; four are ca- 



nines — 1. e 

 1 — 1 



3-3 

 one on each side above and below, c. = 



sixteen are premolars — i. e., four on each side 



above and below, pm. 



and twelve are molars 



-i. e., three on each side above and below, m. = 



3 — 3 



But, as the bilateral symmetry is always perfect in the 

 teeth, there is no necessity to express but one side— i. e., 

 all the teeth as seen from one side, as in all the formulas, 

 except the first two. 



The normal number, we have said, is forty-four. 



