CHAPTER X. 



The Rabbit's Appendix. 



Undoubtedly the largest and most highly specialised 

 subepithelial lymphatic gland occurs not in man but in 

 the rabbit. The rabbit's vermiform appendix is the 

 particular example taken but the proximal and distal 

 ileo-csecal patches, though smaller in bulk, present a 

 similar complexity of structure. (Fig. 23.) 



The rabbit's vermiform (i.e. of similar even cylin- 

 drical shape to a worm) appendix measures several 

 inches in length and J in. to |^ in. in transverse section. 

 The wall of this tube feels quite thick. From the 

 peritoneal aspect it is often possible to see with the 

 naked eye the independent lymphoid nodules (really 

 the deeper layer of these) of about the size of a pin's 

 head. Occasionally each nodule is outlined by a just 

 perceptible row of black dots. On the mucous aspect 

 can be seen the orifices of the calyx-like glands. 



When a transverse section is examined under a low 

 power it is seen that, whereas in man the lymphoid 

 layer rarely forms as much as one-half of the mural 

 thickness, in the rabbit the lymphoid coat constitutes 

 up to nine-tenths, of the total thickness and the mus- 

 cular coats have come to appear relatively as a very 

 narrow band in the section. (Fig. 24.) 



The lumen of the appendix is filled with bacteria 

 most of which are gram-positive and of unusually large 

 size. Particles of partially digested vegetable food can 

 be distinguished. Glandular lymphocytes are often to 

 be seen in the lumen. These can easily be shown to 

 contain ingested bacteria. 



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