MORPHOLOGY OF THE VERTEBEATA. 



> ALIMENTARY TRACT. 



Teeth are developed upon the mucous membrane covering the 

 palato'-quadrate cartilage and the mandible: these are never 

 implanted in sockets. 



The basis of the tongue is composed of the glossohyal bone, and 

 its surface is smooth and devoid of papillae. There are no 

 salivary glands or tonsils, but mucous follicles pour their secretion 

 into the mouth. The entry to the gullet is simply constricted by 

 a sphincter muscle. 



The oesophagus is a short and wide canal, with a thick muscular 

 coat; its mucous membrane is longitudinally folded to allow of 

 increased capacity for unmasticated and often very large food. 

 It is not uncommon to find a large-sized fish in the stomach in 

 specimens after death. Numerous recurved processes project 

 from the inner surface of the oesophagus. 



The stomach is simple, and is a large extensive sac, with a great 

 disproportion in size of cardiac and pylorice orifices. The inner 

 surface is rugose at the cardiac end : a circular pyloric valve is 

 Well developed. The intestinal canal is shorter than the body 

 itself. The true homologUe of the small intestine is extremely 

 narrow and short. It loops upwards from lower end of stomach, 

 and receives the ducts of the liver and, pancreas. Beyond the 

 openings of these ducts it suddenly expands into the large 

 intestine, which is straight and very short in proportion to the 

 length of the body, and is continued to the anus, which opens . 

 into the fore part of the cloaca. 



To recompense for the great shortness of the intestinal canal, 

 the absortive area of the mucous membrane of the large intestine is 

 increased by being raised into spiral transverse folds, forming the 

 So-called "spiral valve," which runs throughout the entire length 

 of the large intestine in a cork-screw-like manner. This spiral 

 valve is both- the homologue and analogue of the valvulse con- 

 niventes of some mammals, man included. 



The stomach and intestines are invested by the peritoneum, 

 and are connected with the dorsal wall of the abdominal cavity 

 by the mesogastric and mesenteric folds of the peritoneum. 



The cavity of the peritoneum is in communication in front 

 with that of the pericardium, to be presently alluded to, and 

 behind communicates with the exterior by two pores. 



THE LIVER 



Is of large proportional size, and is remarkable for the great 

 quantity of fine oil in its substance. It,is attached at the fore 

 part of the abdomen W£m e $j^?M M[, partitioning off the 



