5)00 THE ORGAXS OF DIGESTION 



nal oblique, and external oljlique. In front, besides tbese muscles, there are the 

 two recti and pyraniidales muscles. External to the peritoneum the abdomen is 

 lined bv a special laver of fascia. 



The abdomen is the largest serous cavity in the body. Its serous membrane is 

 the peritoneum, which, through its various complicated arrangements, is always 

 (with one uninii)ortant exception) a closed sac, so that the viscera are in reality 

 situated outside tlie enclosure. The principal viscera found in the al)d(>nien are 

 those connected with digestion and the excretion of urine. 



On freelv laying oi)en an abdomen from the front, the general form of the s]iace 

 is seen to be an" irregular hexagon, the sides of which are formed as follows: — The 

 upper two by the niargins of the costal cartilages with the ensiform cartilage 

 between; the 'two lateral sides by the edges of the lateral boundary; and the two 

 lower by the two ligaments of Poupart which meet at the pubes. 



In this irre<rular hexagon the following organs can be observed without dis- 

 arrauizing their' normal position (fig. 565). Above, on the right side under the 

 costal cartilages, can be seen the liver, which extends from the right across the 

 median line to a point below the left costal cartilages. Below the liver, and lying to 

 the left side, can be seen the anterior surface of the stomach; from the lower 

 border of the stomach the omentum extends downwards, and shining through it can 

 be seen the middle part of the transverse colon. On each side and below the irregu- 

 larly folded omentum are exposed the coils of the small intestine; in the right iliac 

 fossa apart of the ca3cum appears; and in the left iliac fossa a coil of the sigmoid 

 flexure is usually evident. 



To the left of the stomach and under cover of the lower ribs of the left side the 

 edge of the spleen may possibly be observed; and just below the edge of the liver, 

 and about the level of" the tip of the ninth rib, the gall bladder may be seen. _ The 

 dome of tlie urinary l)ladder may be noticed just beliind the symphysis pul^is and 

 in the median line. The disposition of the viscera in the foetus is shown in fig. 578. 



THE ST03IACH 



General description. — The stomach is situated in the upper part of the abdo- 

 minal cavity and to the left side, ^^'hen empty it is found in the left hypochon- 

 drium and left half of the epigastric region. Above it are the liver and diaphragm, 

 while below is the transverse colon. It is somewhat pyriform in outline, Avith the 

 small end of the figure twisted upward. Its length is about twelve inches, and its 

 width four to five inches. The distance between its two orifices varies from three 

 to six inches. Its average capacity is about five pints (two to three litres). It 

 weighs four ounces and a lialf. 



There are two orifices, two borders, and two surfaces to be noticed. The left, 

 splenic, or cardiac end of the viscus is much expanded, and forms the great rul-de- 

 snc or fundus. At the right or pyloric end there is another slighter ex])ansion, 

 called the antrum pylori or small cul-de-sac (fig. 566). 



The cardiac orifice, by which the oesophagus opens into the stomach, is situ- 

 ated about three inches from the left extremity, owing to the bulging to the left of 

 the great cid-de-sac. Tlie pyloric orifice, or pylorus, is situated to the extreme 

 right, and is more anterior in i)osition tlian the canHac orifice. 



The pylorus is jiroduced ])y a thickening of the visceral walls l)etween the duo- 

 denum and stomach. The circular muscular fibres which surround the stomacli 

 are here thickened into a strong ring, thus forming a sphincter which can be felt 

 from the outside. The longitudinal fibres pass over the circular fibres, and are not 

 generally supposed to take ])art in the thickening. The mucous membrane is 

 pushed in by the muscular ring and also thickened. The pyloric opening will 

 hardly admit a sixpence, its fullest diameter being about one-half of an inch 



