I4 8 THE VITAL PROCESSES 



The muscular coat consists of three separate layers which 

 are named, from the direction of the fibers, the circular 

 layer, the longitudinal layer, and the oblique layer (Fig. 69). 



Oblique layer 



Cardiac orifice 



Pylorus 



FIG. 69. Muscles of the stomach (from Morris' Human Anatomy). 

 The layer of longitudinal fibers removed. 



The circular layer becomes quite thick at the pyloric orifice, 

 forming a distinct band which serves as a valve. 



The outer coat of the stomach, called the serous coat, is a 

 continuation of the peritoneum, the membrane lining the 

 abdominal cavity. 



Stomach Digestion. In the stomach begins the defi- 

 nite work of dissolving those foods which are insoluble in 

 water. This, as already stated, is a double process. There 

 is first a chemical action in which the insoluble are changed 

 into soluble substances, and this is followed immediately 

 by the dissolving action of water. The chief substances 

 digested in the stomach are the proteids. These, in dis- 

 solving, are changed into two soluble substances, known as 



