THE HORSE. 



sets of teeth ; those appearing first are known as the tem/porary^ 

 deciduous^ or milk teeth, and are succeeded by the permanent 

 set. On comparing tlie different magnitude of the jawbones of 

 the colt and the adult horse, the necessity of such a change is 

 at once apparent. By it the teeth are adapted to the size of 

 the maxillary bones. The teeth, from their peculiar character 

 and mode of growth, do not admit of any material increase of 

 dimension, and nature was therefore forced either to place the 

 large permanent teeth in small and disproportiona^te jawbones, 

 or to ada])t the size of the teeth by displacement to the growth 

 of the bones that contained them. The latter jirocess is adopted, 

 and constitutes one of those remarkable evidences of creative 

 power, with which the living frame is replete. 



" Three substances enter into the structure of the teeth ; 

 1. The enamel. 2. The dental bone, or ivory ; and 3. A corti- 

 cal envelope, surrounding the fang. The enamel differs but 

 little in chemical constitution from the osseous body of the 

 teeth, and that principally results from the absence of animal 

 matter in it. It ai3pears closely analogous to the univalve por- 

 celainous shells, and is the hardest and most indestructible sub- 

 stance of the body. The dental bone is distinctly tubular in 

 structure, as was first demonstrated by Lenwenhoeck, in a com- 

 munication made by him to the Philosophical Transactions of 

 1GT8, and this has been confirmed by the late microscopical re- 

 searches of Purkinje and Muller. These tubuli take a pci-pen- 

 dicular direction, and are exceedingly small, but capable of 

 absorbing ink by capillary attraction. No such tubuli have 

 been traced in the enamel. The teeth, both incisors and grind- 

 ers, are being constantly worn away at the crown, but the loss 

 is supplied by the gradual, continuous and equivalent growth 

 from the root. The horse's teeth are sometimes, but not fre- 

 quently, subject to disease. It is seldom that any of them are 

 lost from age, as is the case with man, and most other animals. 

 Blaine, in his Outlines of the Veterinary Art, p. 40, 4th edition, 

 institutes the following comparison between the respective ages 

 of man and the horse. 



"The constitution of horses and men may be considered as 

 in an equal degree of perfection and capability of exertion, or. 

 of debility and decay, according as youth or age preponderates. 



