DIGESTIVE SYSTEM. 345 



twenty to thirty times round it. The small intestine 

 opens into the side of the caecum about an inch 

 from its proximal end, a large Peyer's patch in the 

 wall of the caecum being continuous with the sacculus 

 rotundus. 



Proximally, the caecum passes directly into the 

 colon, while distally it ends blindly in the thick- 

 walled finger-like vermiform appendix. This latter 

 is about four inches long, and its walls resemble 

 Peyer's patches in appearance and structure. 



In the rabbit the caecum is of enormous size, as 

 in most herbivorous mammals with simple stomachs. 



7. The colon is about a foot and a half in length. The 



first part of it is very markedly sacculated, the 

 sacculations lying in three longitudinal rows, 

 separated by smooth areas of unequal width. 

 Towards the rectum the walls become smooth. 



8. The rectum or terminal portion of the intestine is a 



narrow tube, about two and a half feet in length, 

 pale in colour, and presenting a moniliform appear- 

 ance, owing to the contained faecal pellets. At its 

 hinder end it passes through the pelvic cavity to 

 the anus. 



Note. Numerous semi-transparent sacs usually occur, 

 attached to the peritoneum in the pelvic and gastric regions. 

 These are the cysts of a Tapeworm, and they develop to 

 maturity in a dog. 



Internal Structure of the Alimentary Canal. 



1. The stomach. 



Slit up the stomach along its posterior surface : wash out 

 its contents, and examine it under water. 



The wall of the stomach consists of an outer 

 peritoneal investment ; a middle muscular layer, 

 thickened at the pyloric end ; and an inner layer of 



