DENTITION AND DENTAL DISEASES 241 



third molars. As a rule, the shells of the milk teeth come off from 

 the lower jaw sooner than from the upper. In many cases when 

 the shells are removed, also in cases of retarded dentition, a foetid 

 smell, as of diseased bone, is noticed, and from the irritation set up 

 in the lining membrane of the mouth, which extends to the throat, a 

 troublesome cough may be induced. 



354. At five years old (8) the corner milk incisors are replaced 

 by permanent teeth, and the canines, or tusks, appear in the horse, 

 but are generally absent in the mare ; occasionally we find small 

 rudimentary tusks in the latter. The horse is now full-mouthed. 



355. With the exception of a young horse casting its teeth, and an 

 old one with unevenly worn surfaces, I am not in favour of giving 

 crushed or bruised oats to horses, as the crowns of the horse's molar 

 teeth resemble the surface of the old-fashioned millstone, being 

 properly adapted for grinding the grain. I therefore recommend 

 oats to be given whole, so that the animal can have the pleasure of 

 grinding them, thereby getting the full benefit of the salivary juices, 

 and their action on the starchy matters of the food. Crushed oats 

 are also more liable to be bolted, and cause stomachic derangement. 



356. The upper molar teeth in horses and cattle are much larger 



and broader than the lower ones. The upper jaw, being a fixture, as 



it were, gives a broader and firmer surface for the rotary movement of 



the lower jaw to act upon ; thereby, in some instances, in aged horses, 



the uneven wear leaves sharp ridges on the outer edge of the upper 



molars and inner edge of the lower : these have to be dressed down 



with the tooth-rasp (Plate XXXIII. , No. 4), to prevent laceration of 



the tongue and inside of the cheeks. Occasionally the teeth become 



elongated and very uneven (particularly the last tooth on the lower 



jaw), and have to be cut by special shears, and in this case I usually 



operate with the animal standing, except when I have a rough 



customer to deal with. (For such an operation nothing beats 



Thompson's instruments, and I would point out that I am not the 



Thompson in question who introduced this useful article.) Molars 



are sometimes split, through getting some hard substance amongst 



the food, and for causing this there is nothing worse than foreign 



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