THE DIGESTIVE SYSTEM OF THE DOG. 547 



thereof. In the stomach this contraction causes the food to be turned round and round, and up 

 and down (there being both circular and transverse fibres in the coat of this organ) until every 

 particle of it is in its turn brought into contact with the walls of that organ, and so receives and is 

 mixed with the gastric secretions, that turn it into chyme. 



In the intestines, where the muscular fibres are circular, contraction alternating with dilatation 

 results in a creeping, worm-like (vermicular or peristaltic) motion, which not only mixes the food, 

 but propels it along the canal towards the anus. 



We see, then, that it is the contact of the food that excites the muscular contraction of the 

 intestinal walls, and propulsion onwards of the bowel's contents. And this is one reason why we 

 give soft, liquid, and non-stimulating food in a case of diarrhoea. Again, any druggist's apprentice 

 knows that a dose of opium or its tincture (laudanum) will cure a case of simple diarrhoea, but for 

 the life of him he could not explain why. The reason is that opium benumbs the nerves, puts 

 them asleep nearly ; at all events renders them less able to act as conductors of animal electricity. 

 They are less easily excited, therefore, by the contents of the intestine, and the vermicular 

 motion is in a corresponding degree checked. But this is not all ; for, for the same reason, the 

 secretions of the bowel do not flow so abundantly, and so the bowel's contents are rendered less 

 fluid. 



The oesophagus begins at the funnel-like pharynx, and ends at the stomach. In the dog 

 it widens out again as it approaches the stomach, and is not only very dilatable, but remarkably 

 muscular. 



The next part of the alimentary canal which demands our attention is the stomach. It 

 is a membranous and muscular bag or pouch. In the dog this is somewhat pear-shaped. The 

 upper opening is called the cesophagal or cardiac, and the lower the pyloric. This latter is 

 surrounded by a concentric band of muscular fibres, a strong ring in fact, which shuts up the 

 lower orifice, until Nature requires it shall be opened. 



The dog's stomach of course differs in size in different breeds, and, upon the whole, it 

 is a very accommodating and capacious viscus, although it is very easily excited to the act 

 of vomiting. There is one other peculiarity about a dog's stomach the muscular fibres are 

 partially under the control of the Voluntary nerves. At all events, it is well known that the 

 animal can vomit at will. This faculty is sometimes, though very rarely, met with in the human 

 race. 



The next portion of the digestive canal begins at the pylorus, and is continued to the anus. 

 It is called the intestine, large and small. The small intestine comes first. It is divided into the 

 duodenum, the jejunum, and the ilium. There is no special need for the reader to burden his 

 memory with these names. They are quite arbitrary, and Chauveau's division, into the first, the 

 fixed or duodenal portion, and the second, the free or floating portion, is better. 



The small intestine is maintained in its position at one extremity by the stomach, at the other 

 by the caecum, and is fixed in the centre by what is called the great omentum, by butchers 

 the apron, which is, in fact, a fold of the peritoneum. 



The peritoneum is the largest serous sac in the body. Serous membranes are sacs or bags 

 which line the closed cavities of the body. Neither their uses nor their positions in the body 

 are difficult to understand. Serous membranes are beautifully designed by Nature to counteract 

 the evil effects of friction. Wherever, then, in the human body two surfaces are opposed to each 

 other, and rub or move against each other, we find a serous sac placed between them. Take 

 a common articulation, for example, or joint. Here you have two surfaces which are opposed to 

 each other, rub against each other, and, but for the interposition of this serous membrane, would 



