38 DESCRIPTIONS OF PREPARATIONS. 



as to form the periphery of the preparation. The centre-point of the 

 preparation and of the figure is occupied by a globular sac, c, the ' sacculus 

 rotundus* the thick walls of which consist of Peyerian follicles, and 

 represent the histologically somewhat similar termination of the small 

 intestine in man. The small intestine dilates to form this sac after de- 

 scribing a siphon-shaped course internal to one formed by the commence- 

 ment of the colon. A saucer-shaped patch, d, similar in structure to the 

 sacculus rotundusy lies immediately to the right of it in the wall of the large 



FIG. 3. (Half natural size.) CAECUM WITH VERMIFORM APPENDIX AND PARTS-OF LARGE 



AND SMALL INTESTINE OF RABBIT (LepUS cuniculus). 



a. Vermiform appendix. 



b. Thin-walled portion of caecum, spirally constricted in correspondence with an internally situated 



spiral valve. 



c. The sacculus rotundus, or dilated globular end of small intestine, with thick walls consisting of 



Peyerian follicles. 



d. Saucer-shaped thickening of wall of large intestine, on the internal periphery of which, not shown 



in this figure, the ileo-caecal valve opens. 



e. Distal end, i. e. segment next caecum, of small intestine in section. 

 f. Proximal end, i. e. segment next caecum, of large intestine in section. 



Attached to the spirally-constricted part of the caecum on its inner edge, just before it passes into the 

 vermiform appendix, we see certain mesenteric glands into which an injection of Berlin Blue has 

 passed, having been introduced by ' Einstichung ' or puncture with a fine syringe into the lacunar 

 spaces surrounding the Peyerian follicles of the vermiform appendix. 



