] 8 DIGESTION AST) FOOD. 



even from trustworthy persons. A supposed cause is assumed, 

 and then retailed as certain. 



PREHENSION OF LIQUIDS. Colin has classified under four 

 heads the various methods adopted by animals in drinking. 

 He considers there are four, 1st, Suction, such as the act 

 of drawing milk by the young animal 2nd, Pumping, by 

 immersion of the lips and action by the tongue within the 

 mouth, on the principle of the common pump. 3rd, Aspira- 

 tion, or the act of inhaling; the vacuum for the introduction 

 of the liquid being produced by a respiratory act, as well as 

 by the mouth. 4th, Lapping. 



In the act of suction the teat is grasped by the lips, and 

 even by the teeth, so that the mouth is closed upon it; the 

 tongue is then pressed against the teat and withdrawn, pro- 

 ducing a vacuum by the action of the tongue and cheeks 

 exclusively, without any respiratory effort. The liquid is 

 swallowed, and. suction again practised. This wise provision 

 preserves the infant, or the sucking animal, from the milk 

 passing into the windpipe, which it might do if inhalation 

 served to draw the fluid into the mouth. 



The act of pumping is that resorted to by the horse. He 

 drops the lips beneath the surface of the water, and sometimes 

 immerses even the nose. A small space between the lips, 

 opened by the rushing in of the liquid owing to the action of 

 the tongue, represents the small aperture through which water 

 is drawn in the act of pumping, and the tongue acts as a piston 

 precisely as in the process of sucking. Poncet performed an 

 experiment to prove that the act of drinking in the horse is 

 not by inhalation, as some persons supposed. He opened the 

 windpipe and introduced a tube into it, as in the performance 

 of tracheotomy, and the animal drank as before, though no 

 inhalatory force could be then brought to bear on the liquid 

 through the mouth. The anatomical relation between the 



