434 NAVIN ox THE HOKSE. 



ossifying within and enamel forming without by crystallization, 

 we have the same process going on within the cavity of the 

 jaw, in five sacks for an upper grinder and four for a lower, 

 as if the intention were to form these respective numbers of 

 teeth. The enamel can be traced around each of these divi- 

 sions, and they would undoubtedly be distinct, but another sub- 

 stance is now secreted, which, being a poAverful cement, unites 

 all into one body, making one tooth. After this, another coat 

 of enamel spreads over the sides, but not over the top, and the 

 tooth is complete. By this disposition of columns of bone, 

 cement, and enamel, a most prodigious degree of strength is 

 obtained, and the grinder is capable of crushing the solid sub- 

 stances constituting the food of the horse. But as the bone 

 and cement Avear away faster than the enamel, a rough surface 

 is always presented, thus enabling the horse to grind oats and 

 corn, for many years, without ever once having to "pick the 

 millstones." The grinders in the lower jaw, being originally 

 •formed from only four bones, are not so large nor so rough as 

 those in the upper jaw. 



The grinders are not placed horizontally in either jaw. In 

 the lower the higher side is within, and gradually shelving out- 

 ward, while in the upper jaw the higher side is without, shelv- 

 ing inward, thus enabling the grinding motion to be performed 

 with the greatest possible facility. Though, to the casual ob- 

 server, a pile of horses' teeth would appear to have but little 

 regularity about them, an experienced hand would readily 

 assign each its proper situation. To the naturalist the study 

 of the teeth of animals is a subject of greatest interest. But 

 as the object of the present work is not to enter into the dis- 

 cussion of the beauties of science, but to furnish such informa- 

 tion as will enable every person to give the horse that intelli- 

 gent attention his worth and nobility deserve, and to detect 

 the tricks and impositions of dishonest dealers, I shall return 

 io the consideration of the changes which take place in the 

 mouth. Observations are made on the teeth of the lower jaw 



