ZOOLOGY. 229 



The Horse. 



A male horse has 40 teeth when he has completed 

 his full number; the mare usually but 36. They are 

 divided into the cutting teeth or nippers, the cuspi- 

 datae or tushes, and the molares or grinders. The 

 age of a horse may be easily known by his teeth, 

 under eight years of age, after which the usual marks 

 wear out. 



Arsenic may be given to horses with impunity to 

 the amount of two drachms troy. White vitriol does 

 not act as an emetic on the horse, which, owing to 

 the structure of its stomach, is incapable of vomiting. 

 Colocynth, which is so purgative to man, has very 

 little effect on the horse. 



A kind of third eye-lid is found in the horse, and 

 called the haw, moistened with a pulpy substance or 

 mucilage to take hold of the dust on the eye -ball and 

 wipe it clean ; so that the eye is hardly ever seen 

 with any thing on it, though greatly exposed from its 

 size and posture. 



Mares, in the language of jockeys, become aged at 

 seven years, horses at eight years. They are both so 

 called until twelve or fourteen years, after which 

 there is a sinking in and about the loins that denotes 

 old age. 



Fishes. 



With respect to fishes, it is probable that a great 

 number of species live in succession on each other, in 

 proportion as they exceed each other in strength, 

 voracity, and activity ; their enormous reproduction 

 being evidently destined to supply any vacuity this 

 devouring system might otherwise occasion. 



The air-bag of some fishes soon loses its muscular 

 power, in consequence of the air being expanded by 

 the action of the sun, when the fish has remained too 

 long at the surface, which it then cannot quit. Some- 

 times, from increased expansion, the air-bag bursts. 



