DISSECTION OF A HAT. 89 



wards (i.e., towards the tail). See how it is attached by 

 mesenteries to a muscular partition (diaphragm) bound- 

 ing the peritoneal cavity in front. See the oesophagus and 

 a blood-vessel (postcava) extending from the liver through 

 the diaphragm. Sketch the alimentary canal. 



Cut through the oesophagus just in front of the stomach 

 and through the rectal portion of the intestine, and cutting 

 the mesentery remove the alimentary canal. 



In the body-cavity see, dorsal to the liver, the kidneys. 

 Are they at the same level ? Covering the anterior end of 

 each kidney is a triangular supra-renal capsule. Trace 

 from each kidney (median surface) backwards a whitish 

 tube, the ureter. In the median line of the body-cavity is 

 the aorta already mentioned. Trace it backwards, finding 

 the arteries (renal) going to the kidneys. Farther back 

 the aorta divides into a pair of common iliac arteries. 

 Trace these into the legs. Do you find them to divide ? 



Just behind the point of division of the aorta into the 

 common iliacs can be seen the common iliac veins, which 

 return from the legs and unite into a vessel, the postcava, 

 which passes forward, at first dorsal to the aorta. A little 

 farther forward the postcava receives an ileo-lumbar vein 

 from either side, and then a renal vein from each kidney. 

 From the kidneys trace the postcava forward through the 

 liver. This may readily be done by cutting away the ven- 

 tral part of the liver and then, inserting the point of the 

 scissors into the postcava, make a cut. Continue this 

 until the whole vessel is laid open up to the diaphragm. 

 On the inner surface of the postcava, inside the liver, notice 

 the openings of the hepatic veins. These bring to the 

 postcava the blood which entered the liver by the portal 

 vein. 



