308 DISSECTION OP THE RABBIT 



a. Peyer's patches are slightly thickened oval spots, 



granular in appearance, and about a third of an 

 inch in diameter, which occur at intervals along 

 the whole length of the small intestine, on the 

 side opposite to the attachment of the mesentery. 



b, The sacculus rotundus is the dilated distal end of 



the small intestine, opening into the side of the 

 csecum about an inch from its proximal end. Its 

 walls have the structure of Peyer's patches. 



6. The caeeiun and vermiform appendix. 



The csecum is a large thin-waUed diverticulum of 

 the alimentary canal, at the junction of small intestine 

 and colon. It is about twenty inches long and an 

 inch or more in diameter, and is marked externally 

 by a spiral constriction which runs 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 waU of the CEecum 

 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 monUiform appear- 

 ance, owing to the contained faecal pellets. At its 

 hinder end it passes through the pelvic cavity to 

 terminate at the anus. 



