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ANATOMY AND PHYSIOLOGY OF THE HORSE. 



horses cut at the same age, thai they have 

 little or no attrition against each other, and 

 that they are worn by the tongue and food, 

 sometimes more, at others less, should lead 

 us to draw conclusions from them with 

 great caution ; in fact, as indications of 

 age, they can only be trusted to when they 

 accord with the incisors. The tush or 

 tusk makes its appearance by the fifth, and 

 is completely evolved by the sixth year. 

 In the seventh, the apex of the cone is 

 worn off. In the eighth, its furrows grow 

 shallow ; in the ninth they arc obliterated. 

 Then the apex gradually wears away , in 

 the twelfth year it becomes round ; from 

 which time, though it gradually becomes 

 shorter, its shape varies but little. But it 

 is not uncommon to see the tush blunted 



like an acorn in the ninth year, nor to find 

 it still pointed in the sixteenth year. 



" Pessina concludes his account of the 

 changes to which the teeth are subject, 

 by observing, that, as they are dependent 

 on wear, which is no law of nature, but 

 an effect of mechanical and accidental 

 causes, they cannot, but under certain lim- 

 itations, be implicitly relied on." 



We are now supposed to be in posses- 

 sion of some of the most important facts 

 tending to elucidate the changes which the 

 teeth undergo ; and, in view of making our- 

 selves more conversant with this subject, 

 we shall re-commence our examinations, 

 for it is a matter of the highest importance 

 that a veterinary surgeon shall understand 

 the method of ascertaining a horse's age. 



EXAMINATIOXS ON THE TEETH. 



Q. Does the evolution of the tush always indicate 

 that the animal is five years of age ? — A. No. It has 

 been seen between the third and fourth years. 



Q. Which teeth do you place the most reUance on 

 in ascertaining the age of a horse ? — A. The side or 

 lateral of the lower jaw. They make their appearance 

 last; their pits are the last to disappear; after the 

 age of eight or nine, however, the pits in the incisors 

 of the upper j aw are also indicative of age; they, being 

 deeper, of course remain some time after all vestiges 

 of the same have disappeared in the lower jaw. 



Q. In adult life is there any continued accretion or 

 after-growth of the teeth? — A. Yes. If it were not 

 so, the animal would, in course of time, have to gather 

 food, and grind the same with liis gums ; for, acccord- 

 ing to the law of iccar and tear, destruction of the in- 

 struments — grinders of food — must more or less reg- 

 ularly take place. 



Q. What changes take place as the horse advances 

 in age, in the inchnation of the incisors ? — A. They 

 acquu-e a horizontal direction. 



Q. How is this change of dhection compensated for 

 in the grinders ? — A. The faces of the latter are worn 

 down by friction, and thus the nippers come in contact. 



Q. Are there not times when the consumption of the 

 faces of the teeth, by friction, is not in proportion to 

 growth, in issue from the socket ? — A. Yes. 



Q. What is the result? — A. The faces of the grind- 

 ers do not come in contact, and the food is, conse- 

 quently, imj^erfectly masticated. 



Q. How is tills rectified ? — A. By sawing off the 

 nippers to their natural length. 



Q. Taking it for granted that there is a time when 

 the teeth cease to grow, how do you account for the 

 lengthy teeth observed in aged horses ? — A. The fang 

 shrinks, and is carried upward in the lower and down- 

 ward in the upper jaw, and the gums also shrinli; thus 

 we get length of teeth. 



Q. What are the general appearances of age, micon- 

 nected with the teeth ? — A. The muscles of the head 

 and face condense, and give to the same a lean appear- 

 ance ; the cavities above the eyes are deep ; the gums 

 and palate become pale and callous ; the submaxillary 

 space is capacious, and gray hairs make their a])pcar- 

 ance in various places ; the neck appears small and 

 Anry, the withers sharp, the back cm'ves, and the 

 limbs appear sinewy. 



