hand, are quite numerous in the respiratory, and especially, the intestinal tract. Groups of follicles may also be found in the lining of the upper ends of these tracts in such situations that the names faucial, pharyngeal, or even tubal tonsils are justly applied. I do not find any reference to a lingual tonsil in birds, but this structure is found, with of course many modifications, down as far as the monotremes. The lymphoid tissue of the nasopharyngeal region is so placed in animals as to be exposed to aerial and food infections, just as it is in man. It is, however, noteworthy that chronic inflammations leading to hypertrophy or to obstruction have not come to our attention. There is only one diagnosis of chronic tonsilitis in our records, a determination based upon the nodular red-brown prominence of the tonsillar region, but there were no true hypertrophy and areas of fibrosis combined with necroses as seen in human medicine; this case concerned a Chacma baboon. HYPERPLASIA. In so far as the reaction to infectious or toxic agents is concerned there seems to be a fairly uniform character through the mammalian groups, but in the Aves there are a few differences worthy of mention. It is at once admitted that these observations upon birds are based upon a very few sections of isolated lymphatic tissue, but they are supported by records of the changes in nodes in mucous membranes and viscera, and by those in the spleen. The first and perhaps most noteworthy difference is in the paucity in birds of large mononuclears of the endothelial type. Their position in chords, sinuses and germinal centres is taken by deeply staining mononuclears, of the size and general character of large lymphocytes as seen in the blood. The hyperplasia in the follicles is much more dense but it is outdone by that in the chords. Since the nodal tissue of birds is not so sharply delimited by some sort of capsule, it is but natural that the hyperplasia should be diffuse; in the intestinal wall it may extend laterally twice or thrice the width of the normal follicle. Necrosis, unless the disease be mycotic, tuberculous or parasitic, is uncommon.