172 THE DOG *$ HEALTH. 



about him and prepare for an independent existence. 

 Every organ of the body becomes by degrees more active, 

 and puppy coat, carriage, form, etc., are gradually ex- 

 changed for those characteristic of the adult of the breed 

 to which he belongs. 



Those familiar with a breed by raising puppies can, 

 with considerable accuracy, estimate the age of a puppy 

 by its general appearance and demeanor, as they can also 

 of an " old dog," though in the latter case with much less 

 certainty. 



It is easier to decide the age of a very young puppy 

 than of a dog of any other age, while it is not possible to 

 determine with any degree of certainty the age of a well- 

 reared dog between his first and his fourth or fifth year. 

 The same reliance can not be placed on the teeth as in 

 the case of the herbivora, especially the horse, in which 

 their rate of wear is fairly constant and their appearance 

 for each year of life up to old age characteristic. The 

 fact is, the dog scarcely uses his teeth to masticate food 

 at all, unless it be in gnawing bones. But considerable 

 dependence may be placed on the teeth to indicate age 

 within the first year of the dog's life. 



It will be borne in mind that a tooth consists of a part 

 imbedded in the gum and jaw, the root or fang, and of an 

 exposed portion, or crown. The latter is capped by an ex- 

 tremely hard substance enamel beneath which is the 

 " ivory " or dentine, made up of fine tubules into which 

 the substance of the pulp extends. The tooth is supplied 

 with blood-vessels and nerves through the pulp, which fills 

 the hollow interior of its root or roots, and corresponds to 

 the marrow of bones in some degree. (Fig. 9.) 



