340 LIFE, IN ITS HIGHER FORMS. 



^\greatest of quadrupeds — between the Mouse and the Ele- 

 phant. Not to speak of the similarity in form of many of 

 their bones, and their jaws formed of parallel laminae, the 

 latter is, like the former, destitute of canines, while its 

 incisors assume a curved direction, and project from the 

 mouth as great tusks. The molars of the Elephant, like 

 those of the Guinea-pig, are composed of a number of ver- 

 tical transverse laminee of bone, each covered with enamel, 

 cemented together by a third substance closely similar to 

 ivory. " This last substance, being much softer than the 

 enamel, wears away faster by the mastication of the food, 

 so that the enamel remains considerably higher, and, in 

 this manner, the surface of each grinder acquires a ribbed 

 appearance, as it originally formed with ridges. From 

 very accurate observations which have been made on the 

 Asiatic Elephant, it appears that the first set of grinders, 

 or milk-teeth, begin to cut the jaw eight or ten days after 

 birth, and the grinders of the upper jaw appear before 

 those of the lower one. These milk-grinders are not shed, 

 but are gradually worn away during the time the second 

 set are coming forward, and, as soon as the body of the 

 grinder is nearly worn away, the fangs begin to be ab- 

 sorbed. From the end of the second to the beginning of 

 the sixth year, the third set come gradually forward as the 

 jaw lengthens, not only to fill up this additional space, but 

 also to supply the place of the second set, which are during 

 the same period gradually worn away, and have their 

 fangs absorbed. From the beginning of the sixth to the 

 end of the ninth year, the fourth set of grinders come for- 

 ward, to supply the gradual waste of the third set. In 

 this manner, to the end of life, the Elephant obtains a set 



