66 THE JERSEY, ALDERNEY AND GUERNSEY COW. 



between three and four; and the next, between four 

 and five, when the full complement of permanent teeth 

 is observed in the mouth. But undoubtedly this erup- 

 tion often occurs far more rapidly. 



The second period of the second dentition is that in 

 which the incisor teeth undergo a manifest change in 

 their wearing aspect, whereby the age of a cow can be 

 told. This period extends from five to nine years of 

 age, and annually each succeeding pair is observed 

 worn down. 



In the third period of the second dentition the form 

 of the teeth completely alters ; the upper surface be- 

 comes progressively narrower and flatter. The teeth 

 become very short and detached from each other, until 

 in extreme old age they fall out. 



In the upper jaw, the ox tribes possess no teeth, but 

 a pad to apply against the incisors. In early life the 

 rudiments of teeth are observed springing from the 

 intermaxillary bone, but a tough fibro-elastic cushion, 

 covered by the firm mucous membrane, becomes con- 

 solidated as the animal acquires age, 



I have not referred to many accidents which affect the 

 regularity of growth and eruption of the worn teeth of 

 cows, but they are very common. Thus a temporary 

 tooth may be prematurely removed when an animal is 

 biting some tough root, or a tooth may be knocked out. 

 The early removal of a temporary tooth does not always 

 ensure the early appearance of a permanent one, and 

 this is seen in some Yorkshire colts which have disap- 



