THE PYLORUS. 39 



direction. They depend upon the contraction of the muscular 

 fibres, and disappear entirely when the stomach is laid open 

 and spread out. 



At the lower orifice is a circular fold, which is permanent, 

 and constitutes the valve denominated Pylorus. It appears 

 like a circular septum with a large foramen in its centre, or 

 like a flat ring. The mucous and cellular coats of the stomach 

 contribute to this, merely by forming the circular fold or ruga ; 

 and within this fold is a ring of muscular fibres, evidently con- 

 nected with the circular fibres of the muscular coat of the sto- 

 mach, the diameter of which at this place is not larger than 

 that of an intestine : the fibres of this ring seem a part of the 

 muscular coat projecting into the cavity of the stomach and 

 duodenum. If a portion of the lesser extremity of the stomach 

 and the adjoining part of the duodenum be detached, and laid 

 open by a longitudinal incision, and then spread out upon a 

 board, the internal coat can be very easily dissected from the 

 muscular, and the pylorus will then appear like a ridge or 

 narrow bundle of muscular fibres, which run across the extend- 

 ed muscular membrane. It is evident that when the parts 

 are replaced so as to form a cylinder, this narrow fasciculus 

 will form a ring in it. Thus arranged the circular fibres can 

 readily close the lower orifice of the stomach. 



The pylorus separates the stomach from the duodenum ; 

 and this separation is marked exteriorly by a small circular 

 depression, which corresponds exactly with the situation of the 

 pylorus. 



The arteries of the stomach are derived from the Cceliac the 

 first branch which the aorta sends off to the viscera of the 

 abdomen. This great artery, immediately after it leaves the 

 aorta, is divided into three branches, which are distributed to 

 the stomach, the liver, and the spleen, and are called the Supe- 

 rior Coronary or Gastric, the Hepatic and the Splenic. 

 Besides the first mentioned branch, which is distributed princi- 

 pally to the neighborhood of the cardia and to the lesser 

 curvature, the stomach receives a considerable branch from the 

 hepatic, which passes along the right portion of its great curva- 



