THE FROG AND VERTEBRATES IN GENERAL 187 



The alimentary canal of the plant-eaters is larger and more 

 specialized than that of the flesh-eaters. This is seen to advantage 

 in certain Ungulates, the grazing cud-chewing animals, or Rumi- 

 nants, such as the Cow and Sheep. In such cases a four-chambered 

 stomach is present and so arranged as to permit the hastily eaten 

 plant tissues, or cud, to be regurgitated for a thorough mastication 

 which is a necessary process if digestion is to occur. From the 

 functional standpoint this condition reminds one at once of the 

 condition already noted in the Bee and Ant which permits the 

 regurgitation of the temporarily stored nectar. 



In Man, the alimentary tract corresponds quite closely to that 

 of the carnivorous animals. From the pharynx the esophagus 

 extends to the muscular sac which constitutes the stomach. The 

 small intestine is greatly coiled and is about 20 feet in length and 

 two inches in diameter. It joins the large intestine, or colon, in 

 the lower right portion of the abdominal cavity. The large intes- 

 tine is about five feet in length and somewhat larger in diameter 

 than the small intestine. It begins with a blind sac, or caecum, 

 to which the tubular vermiform appendix is attached. The 

 latter is a closed sac, normally about four inches in length, appar- 

 ently non-functional, and often the seat of a serious infection, 

 appendicitis. From the caecum the large intestine runs first ante- 

 riorly (ascending colon), then crosses to the left side of the body 

 (transverse colon) and, finally, proceeds posteriorly (descend- 

 ing colon) and dorsally through the short straight rectum to the 

 anal opening. (W. fs. 109, 110.) 



Functional. While the food of adult Frogs normally consists, 

 for the most part, of small living animals, such as Insects or Worms, 

 it is known that they will readily devour almost any kind of food 

 which they can get into their mouths. They are cannibalistic, and 

 a large Frog will devour smaller individuals when the opportunity 

 presents itself. The structure of the tongue, as previously noted, 

 is of such a character that the posterior end of it can be very 

 quickly thrust out from the mouth. The Frog is able to capture 

 even a rapidly moving Insect with this peculiar weapon. In such 

 cases, after contact has been established, the prey is held to the 

 tongue by a sticky secretion and drawn back into the mouth. 



The ingested food is passed directly from the mouth, through 

 the esophagus, and into the stomach where, in the Frog, the first 

 stage of digestion begins. The movement of the food throughout 



