436 



NAVIN OX THE HOESE. 



tinct, and in the others will hare undergone an evident change, 

 and the nippers will meet on their flat crowns. 



At the age of two years the middle pair are quite smooth, and 

 the next pair present very nearly the same 

 marks the first did at one year old, and 

 ,the corner ones have a faint mark. About 

 Ithis time, also, a fifth pair of grinders in 

 each jaw wdll come out. 



About this time another change is pre- 

 paring to take place. The jaw or maxil- 

 lary bones are increasing, and though the 

 milk-teeth, at the completion of the colt's mouth, were sufficiently 

 large to fill it, and as strong as necessary for preparing any food 

 suitable for the young animal, they will soon be found neither 

 broad enough to fill the jaw, showing spaces between them, nor 

 stron2: enouo-h for the mastication of the coarser and harder 

 food which the animal requires. Nature has made provision 

 for these necessities, and has provided for a new set of teeth, 

 larger and more substantial than the first, as we have before 

 seen in the germ, from which they are developed, being placed 

 in the cavities in the jaw beneath those from which the tem- 

 porary teeth were developed while the animal was yet unborn. 

 It is of some importance to understand the process by which 

 the temporary teeth are replaced by the permanent set. It is 

 a well-known principle that if a constant pressure, however 

 light, be kept up on any organized substance, it will be found 

 to waste away at the point where the pressure is applied, or, 

 as it is called, will be absorbed. The same little vessels which 

 run through every organized substance to carry off the worn- 

 out particles, and which are called absorbents, in this case 

 carry off, also, the particles against w^hich the pressure is made. 

 I will illustrate this by a few facts. A wen on the head, 

 though a A^ery light thing, remaining for years, will cause a 

 portion of the solid bone under it to be absorbed. And if the 

 skull is examined after death, a little pit, or depression, will be 



