96 dr richard j. a. berry. 



Summary of Eesults. 



As regards the animals examined, with the exception of the 

 cold-blooded animals, the skate and the frog ; animals which 

 are notoriously difficult of classification, such as the marsupials 

 and the sloths ; the hedgehog, a hibernating animal without a 

 caecum, and the Patagonian Cavy, the caeca of all are charac- 

 terised by large amounts of lymphoid tissue. 



The lymphoid tissue is either specially aggregated together in 

 distinct and definite masses, and more especially is this the case 

 when the Cccca are short, as in the cat and the pigeon ; or else 

 it is diffused throughout the total length of the caecum, 

 particularly when this structure is long, as in the domestic 

 fowl, the pig, and the sheep. 



In all instances the lymphoid tissue tends to be better marked 

 at the caecal apex, or at all events very near the caecal apex, as 

 in the mouse and the rat. 



In the majority of the animals examined, the amount of 

 lymphoid tissue contained in the caecum is largely in excess of 

 that contained in other parts of the large intestine. The line 

 of demarcation between the two is in many instances, such as 

 in the pigeon, the rabbit, the cat, the mouse, the rat, the dog, 

 the striped hyaena, etc., most abruptly marked. The cfficum is 

 thus in warm-blooded animals and the higher vertebrates 

 generally a special seat of lymphoid tissue. 



Proceeding a stage further, it is known that the vermiform 

 appendix of Man represents the true apex of the caecum 

 (Treves, 5 ; Berry, 6). It is further proved beyond all doubt 

 that the characteristic feature of the normal human appendix is 

 lymphoid tissue (Piibbert, Clado, Kelynack, and Fowler) ; and the 

 facts now adduced, and added to the foregoing, point to the 

 conclusion that the histological homologue of the human 

 appendix is to be found in the caecum of the lower animals. 



It has been shown in the present work that the precise seat 

 of the lymphoid tissue in the caecum varies somewhat in the 

 different animals. In the pigeon it occupies the entire ctecal 

 wall. In the mouse and the rat, the lateral wall of the crecum 

 near its apex. In the majority of the animals examined, it 

 occupies the caecal apex itself ; whilst lastly, in the higher 



