MODES OF DRINKING. 197 



lips before a vacuum is created by the withdrawal of the 

 tongue. 



Some animals seem to drink by the suction of the thorax 

 that is, by the enlargement of the chest while the extremity 

 of the head is plunged under water. Thus, while the pig at 

 times drinks quietly by the suction of the mouth, at other 

 times he draws the water into his mouth mingled with air by 

 snatches, with much gurgling noise. 



The dog, like other carnivorous animals, cannot immerse 

 the extremity of the head so as to cover the corners of the 

 mouth without plunging the nostrils also under water ; hence 

 the dog laps the water in drinking. In lapping the tongue is 

 used like a spoon ; the tongue is plunged into the water and 

 quickly withdrawn, being at the same moment curved and ren- 

 dered hollow on its upper surface, and thus a portion of the 

 water is at each such movement thrown into the mouth.* 



The organs in which the aliment undergoes important 

 changes before becoming fit for the repair of the blood, or for 

 the maintenance of animal temperature, are 1, the mouth ; 2, 

 the stomach or stomachs ; 3, the duodenum, subservient to the 

 changes in which are the liver and pancreas ; 4, the intestinal 

 villi ; 5, the mesenteric glands ; and, lastly, the lungs. When 

 the aliment is only to serve for the maintenance of animal 

 temperature, it appears to pass from the stomach and upper 

 part of the intestinal tube into the blood of the portal vein 

 for transmission through the liver, and thence to the right 

 side of the heart, to be conveyed to the lungs, where it under- 

 goes a slow combustion. 



The greater or less comminution by the teeth, and mixture 

 with the saliva and the secretion of the mucous membrane, 

 are the operations to which the aliment is subjected in the 

 mouth. The required comminution varies much in different 



* See Colin, 'Physiologic des Aniinaux Domestiques,' tome i. p. 411. 



