1903.] Meckel's diverticulum in birbs. 353 



are embedded very numerous and large masses of lymphatic tissue, 

 these latter also being more scanty towards the extremity of the 

 gland. All the specimens that I have been able to examine were 

 obtained from bii'ds that had been dead at least for some houi'S, 

 and the lining epithelium was partly decomposed and mixed 

 with the contents of the lumen. 



Text-fig. 44. 



Meckel's diverticulum in the Woodcock. Part of a lonptudiual section of the wall : 

 the lower half of the section shows the intestinal epithelium thrown into 

 a-laiidular folds, with catches of lymphatic tissue ; the upper part shows 

 long-itndinal aiid circular itiuscle-fibres and connective-tissue stroma, with 

 islands of Ij^mphatic tissue. 



There can be no doubt from the structure of this organ that it 

 is a definite gland, but we are so profoundly ignorant of the 

 physiological processes in all animals, except Man and a few- 

 creatures commonly used in experimental laboratories, that there 

 are practically no data foi- making even a suggestion as to its 

 function. It is obviously similar in structure to the paii'ed caeca 

 in certain birds, as, for instance, most of the Passei'es, where these 

 ai'e gla,ndular nipples. It is intei'csting to note that the glandular 

 condition of Meckel's diverticulum occurs in birds that are other- 

 wise specialised and does not appear to occur in birds which in 

 other features of their anatomy are archicentric or primitive. 

 This supports my inference that the glandular condition is a new 

 featui'e, probably of recent origin in the history of birds. 



Pboc. Zool. Soc— 1893, Vol. II. No. XXIII. 23 



