246 



VETERINARY LECTURES 



is frequently cast before the first, but, as a rule, they are generally 

 shed together at ages varying from one year and nine months to two 

 years and three months. The second upper temporary premolar (6) 

 is usually replaced by a permanent one, between two years and three 

 months and two years and nine months. The third inferior temporary 

 premolar is remarkable in having three distinct sections, or columns 

 (Plate XXXII., C, 3), and resembles the sixth permanent ; it is very 

 much larger and longer than the second, and is cast (7) between two 

 years and three months and two years and nine months. Shortly after this 

 (8) the third superior premolar is shed. I have seen the third 

 superior premolar come off before the second, and have also removed 

 them both together {Plate XX XII., B, 2 and 3). 



363. The following plate, representative of one side of the under 

 jaw, shows the age when the permanent molar teeth are cut 

 and when the three first temporary premolars are cast and 

 replaced by permanents : 



P.M., 2 years 3 months to 2 years 9 months 



P.M., from 1 year and 



9 months to 2 years 



and 3 months. 



6.P.M 



T.M. 

 T.M. at birth. 



P.M. at 6 months. 



P.M. at 15 months. 



T.M.— Temporary Premolars. P.M. at 2 years. 



P.M. — Permanent Molars. 



Fig. 12. --Permanent Premolars and Molars of the Cow. 



