THE FROG 



a larger opening is found, leading to the oesophagus, which empties into 

 the stomach. The stomach itself is crescent-shaped, lying mostly on the 

 left side of the body. The larger anterior portion is called the cardiac 

 end ( ), while the constricted or posterior portion, 



meeting with the intestine, is known as the pyloric ( ) 



end. 



msnt. 



Fig. 



A. A Diagram of a Transverse 

 Section Through the Ileum 



.of a Frog. 



c.m M Circular muscle layer ; c.t., 

 submucosa ; ep., epithelium which 

 lines the gut ; l.m., longitudinal 

 muscle layer ; msnt., mesentery ; 

 per., peritoneum ; rid , longitudinal 

 ridges of ileum composing mucosa. 



B. A Portion of the Section Shown 



in A, More Highly Magnified. 

 b.v., Blood vessel ; c.t., connective 

 tissue of mucous membrane or sub- 

 mucosa ; c.m., circular layer of mus- 

 cle fibres ; ep., epithelium ; g.c., 

 goblet cell ; l.m., longitudinal layer 

 of muscle fibres ; let., "lacteal" or 

 lymph vessel of the intestine ; leu. r 

 leucocyte or lymph corpuscle ; p ., 

 peritoneal epithelium. (After 

 Bourne. ) 



The first portion of the intestine, a sort of U-shaped band, is 

 known as the duodenum ( ). The several coils fol- 



lowing it are the intestine proper. This intestine finds its way into a 

 large but short chamber known as the rectum, which in turn communi- 

 cates with the exterior through what is called the cloacal opening- 

 ( ). The walls of the stomach are composed of five 



layers (Fig. 7), the outer portion quite thin, called peritoneum, then two- 

 muscular layers, the outer being called the longitudinal, and the inner 

 the circular muscle layer, followed by a spongy division called the sub- 

 mucosa and an inner folded mucous layer, the mucosa itself. This latter 

 is made up of glands lying in connective tissue. These glands are longer 

 at the cardiac than at the pyloric end. The inner layer of the intestine,, 

 the mucosa, is considerably folded and consists of absorptive and goblet 

 cells. The urinary bladder, reproductive ducts and rectum, open into 

 the cloaca. 



The digestive glands themselves are the pancreas and liver, the for- 

 mer lying immediately between the duodenum and the stomach. It is a 

 much branched tubular gland, secreting an alkaline digestive fluid and 



