40 COMPARATIVE ANATOMY 



tion with the lymph-space. This last communicates with the 

 general system of lymph spaces in the body, which, in their 

 turn, communicate, by means of two pairs of small pulsatile 

 vesicles called lymph hearts, with the blood system. One pair 

 of lymph hearts lie just behind the transverse processes of the 

 third vertebra, the other pair alongside of the urostyle. 



Thus we see that the ccelom, though it does not contain 

 blood, is, in a roundabout way, in communication with the 

 blood-vessels. 



The most obvious organ, when the body-cavity is opened, is 

 the gut, with its great glandular appendages, the liver and 

 pancreas. The buccal cavity passes into a wide tube, the 

 gullet or oesophagus, which passes straight backwards under- 

 neath the vertebral column in the anterior part of the body, 

 narrowing somewhat as it goes. It then widens out again 

 rather suddenly to form a pear-shaped sac with rather stout 

 muscular walls — the stomach. At the end of the stomach a 

 distinct constriction — the pylorus — marks the commencement 

 of the small intestine, the first portion of which, known as the 

 duodenum, is bent sharply forwards so as to lie parallel to the 

 stomach, to which it is attached by a membranous fold — the 

 gastro-duodenal omentum. In this fold lies a small whitish- 

 yellow elongated mass — the pancreas — which will be described 

 farther on. 



The small intestine bends sharply back again towards the 

 posterior end of the animal, is thrown into several loops — its 

 total length when straightened out being from four to five 

 inches, — and then it passes suddenly into a much wider tube 

 about an inch and a quarter long, the large intestine. The 

 large intestine passes without any obvious line of demarcation 

 into a short terminal portion, the cloaca, which opens to the 

 exterior by the anus. A large thin-walled sac, the urinary 

 bladder, opens into the ventral side of the cloaca, which receives 

 other ducts connected with the kidneys and reproductive 

 organs, to be described farther on. 



In order to examine the oesophagus, stomach, and intestines, 

 it has been necessary to turn aside a large lobulated reddish- 

 brown organ which occupies the ventral region of the anterior 

 half of the abdominal cavity. This is the Liver. It consists of 

 three main lobes, a right, a left, and a median, united across 

 the middle line by a comparatively narrow bridge of liver 



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