THE TEUE C^CAL APEX, OR THE VERMIFORM APPENDIX. 89 



be^such a necessary part of the animal economy in cold-blooded 

 animals as in warm-blooded animals. The subject is one which 

 requires a further investigation. 



AVES. 



Of birds, as has been described, the pigeon formed the type. 

 The other birds whose caeca have been examined are as fol- 

 lows : — 



Bernicla juhata, the maned goose. 



Polioaetus 2)lumheiis, the plumbeous fish eagle. 



Leptoptilns javanicus, the Javan adjutant. 



Gallus domesticus, the domestic fowl. 



Anser, the common goose. 



The microscopic appearances presented by the cseca of the 

 maned goose, the fish eagle, and the Javan adjutant all resemble 

 the type, inasmuch as in all of them lymphoid tissue constitutes 

 the predominant feature of the specimen ; they further resemble 

 the pigeon, inasmuch as in all of them the lymphoid tissue is 

 more especially well marked in the caecum, as opposed to the 

 remainder of the intestinal canal. This discrepancy is least 

 marked in the Javan adjutant, though even here it constitutes 

 a noticeable feature of the specimen. 



In the domestic fowl and the common goose there are two 

 long cffica. These are diagrammatically represented in figure 3, 

 which also shows the sites of the various sections. 



In the domestic fowl a high magnification reveals the fact 

 that the lymphoid tissue is diffused throughout the mucosa of 

 the specimen. This is represented in PI. IX. 11. This diffusion 

 of the lymphoid tissue throughout the mucosa in the caecum of 

 the domestic fowl is almost what might be expected, considering 

 the much greater length of the caeca in the fowl as compared 

 with the short caeca of the pigeon. Even in the fowl, this lym- 

 phoid tissue is slightly more marked at the apex of the caecum, 

 notwithstanding its length, as is shown in PI. IX. 11, which is 

 a longitudinal section through the caecal apex. In this plate it 

 will be noticed that there is a greater amount of leucocytal 

 tissue at the apex of the caecum (that is, the lower part of the 



