OCR Text |
Show 1903.] MECKEL'S DIVERTICULUM IN BIRDS. 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 birds that had been dead at least for some hours, 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 longitudinal section of the wall: the lower half of the section shows the intestinal epithelium thrown into glandular folds, with patches of lymphatic tissue; the upper part shows longitudinal and circular muscle-fibres and connective-tissue stroma, with islands of lymphatic 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 M a n and a few creatures commonly used in experimental laboratories, that there are practically no data for making even a suggestion as to its function. It is obviously similar in structure to the paired ceeca in certain birds, as, for instance, most of the Passeres, where these are glandular nipples. It is interesting to note that the glandular condition of Meckel's diverticulum occurs in birds that are otherwise specialised and does not appear to occur in birds which in other features of their anatomy are archicentric or primitive. This supports m y inference that the glandular condition is a new feature, probably of recent origin in the history of birds. P R O C . Z O O L . Soc-1893, V O L . II. No. XXIII. 23 |