134 INTRODUCTION. 



The stomach (fig. 133) is divided into a cardiac and a pyloric portion. 

 The oesophagus, a, opens into the cardiac portion, b ; the pyloric portion, 

 c (which is thicker and more muscular than the cardiac), is that nearest to 



the intestinal canal, and opens into it, by 

 an orifice, termed the pylorus, or pyloric 

 orifice, at the point, d; an aperture provided 

 with strong circular fibres, which, by their 

 action, close it up during the continuance 

 of the process of digestion. 



In the Carnivora, the stomach is simple, 

 and lined throughout by a mucous mem- 

 simpie stomach. -a, the oesophagus; j, the brane ; but, in Man, and most animals with 



cardiac portion of the stomach ; c, the pyloric 



portion; d, the pylorus ; e, the duodenum, or a Simple Stomach, a slight COntraCtlOtt 



commencement of the intestinal canal. i i i i i T J 



marks the division between the cardiac and 



pyloric portions. In the cardiac portion of the stomach, to which the 

 food is first conveyed, it undergoes its preparatory digestive operation, and 

 is gradually transferred from that to the pyloric portion, which is the true 

 digestive division of the stomach. In many animals the cardiac portion is 

 a receptacle, in which the food may be softened, previously to its gradual 

 transmission to the pyloric portion, rather than a laboratory. Hence, 

 in many animals, as the Hare, the Water-rat, the Hamster, &c., the 

 cardiac and pyloric portions are so divided as to communicate by a 

 narrow channel, through which the food is transmitted by the muscular 

 action of the cardiac portion, which is lined with a smooth cuticular 

 membrane, or epithelium, while the pyloric portion is coated with the 

 normal villous membrane. 



In the Horse, the Hippopotamus, the Hyrax, &c., the left, or cardiac 

 portion, is lined with a thick, white, epithelium, having an abrupt mar- 

 ginal termination at the commencement of the villous lining of the pyloric 

 portion. Among the Edentata, the stomach of the Manis presents a 

 similar structure. 



In many animals, piscivorous, and purely herbivorous, the stomach is 

 much more complex than in the animals above noticed ; and, instead of 

 being simply divided by a constriction into two parts, is separated into 

 various compartments, or has, appended to its cardiac portion, various 

 sacculi, or supernumerary cavities, for the maceration of the food before 

 entering that of the pyloric division. 



In the true Cetacea the stomach consists of several compartments, 

 succeeding from the left to the right, and communicating with each 

 other by means of narrow orifices. Among these divisions, it is the 

 first, or left, info which the oesophagus (which is short and spa- 

 cious) directly opens ; the last is the true pyloric portion. Cuvier 

 estimates the number of these compartments to be four ; Meckel, three ; 



