DISSECTION OF THE DOG 15 



Cavum abdominis. — The bony boundaries of the abdominal cavity are 

 incomplete. Dorsally, the lumbar and sacral vertebrae with their transverse 

 processes are covered by the thick muscles of the back. At the cranial end of 

 the cavity some of the ribs and their cartilages form a girdle round the abdomen, 

 while the pelvic bones serve the same purpose at the caudal end. Otherwise the 

 lateral and ventral walls are formed by soft structures only. The ventral wall, 

 much longer than the dorsal, slopes downwards from the pubes to the xiphoid 

 process of the sternum, the steepness of the slope differing in different breeds. 



For descriptive purposes it is necessary to divide the general abdominal 

 cavity into the peltric cavity and the abdomen proper. The plane of separation 

 is on a level with the promontory of the sacrum, the ilio-pectineal lines and 

 the cranial border of pubes. It is, therefore, oblique to the long axis of the 

 abdomen proper, inasmuch as it slopes caudalwards from the sacrum to the pubis. 



Though of questionable utility, the abdomen proper may be subdivided 

 into nine regions by four imaginary planes — two transverse to the long axis 

 of the body and two parallel to the median plane. One of the transverse 

 planes cuts the abdomen on a level with the most caudal part of the twelfth 

 rib. The second transverse plane is parallel to the first and is taken on a level 

 with the lateral angle of the ilium. Thus the abdomen is divided into three 

 transverse zones which may be named subcostal, umbilical, and hypogastric. 



The two longitudinal planes of subdivision are parallel to the median plane 

 of the body and are imagined as occurring on a level with the mid-point of the 

 distance between the lateral angle of the ilium and the symphysis pubis. The 

 longitudinal planes subdivide each transverse zone into three regions as follows : 



/- Right hypochondriac region. 

 Subcostal zone. \ Epigastric region. 



C Left hypochondriac region. 



/ Right lumbar region. 

 Umbilical zone. < Umbihcal region. 



C Left lumbar region. 



r Right iliac region. 

 Hypogastric zone. j Hypogastric region. 



(. Left iliac region. 



' Contents of the Abdomen Proper. — The organs lodged within the 

 abdomen are numerous and serve widely different physiological purposes. 

 They may be tabulated as follows : 



/Stomach. 

 Small intestine. 

 (1) Ahmentary organs. I Large intestine. 



Liver. 

 Pancreas. 



