320 DISSECTION OF THE BABBIT 



3. The caecum. 



Remove the ccecv/m from the iody, cutting across the small 

 intestine and the colon about an inch from it. Take the 

 ccBCum to the sink, and slit it open longitudinally : wash 

 freely, and examine under tvater. 



The inner surface is papillose, and raised along 

 the line of the external constriction into a prominent 

 spiral fold, a quarter of an inch or more m width. 

 The opening from the sacculus rotundus is small and 

 circular ; that into the colon is much larger. 



Cut the vermiform appendix across to see the thickness of 

 its wall ; and slit it open to examiine its inner surface, which is 

 similar to that of Peyer's patches, but with smaller follicles. 



4. The colon. 



Slit open part of the colon ; wash ; and examine under 

 water, noting the papillose surface and the sacculations of the 

 wall. 



5. The rectum. 



Examine a part of the rectum in a similar manner, and 

 note its smooth mucous membrane. 



V. THE THOBACIC VISCEBA. 



Open the thorax by a transverse.incision just in front of 

 the diaphragm: cut through the ribs along each side, and 

 remove the front wall of the thorax as a triangular piece, 

 taking great care not to injure the vessels and other structu/res 

 beneath it. 



Identify and examine the following parts without any 

 further dissection. 



1. The thymus is a pale, soft, glandular-looking body in the 



anterior part of the thorax. It is very variable in 

 size, being larger in the young animal, and some- 

 times extending back so as to overlap the heart. 



2. The heart, enclosed in the thin transparent pericardium, 



lies in the middle of the thorax : it is dark in colour 



