The nature of inflammations of the nasopharynx suggests at once that there may be some anatomical reason for their distribution and character. A general review of the anatomy of the mammalian and avian nasopharynx reveals the relatively greater space in the former, especially in the passage from the nose to the pharynx, and emphasizes the exposure of the opening of the upper larynx in the bird, lying as it does in the posterior part of the tongue and surrounded by the constrictores glottidis. A dissection of the accessory nasal sinuses exposes the relatively large size of these spaces in the lower mammals, and the capacious openings into the nasal cavities.[20] In the Primates and Lemures the anatomy more closely resembles that of man, the sinuses being relatively smaller and the communicating passages narrower. In the bird on the other hand, while the sinuses may be extensive in some they are usually small, yet in all the communication with the turbinate area is by a narrower slit or tortuous canal, frequently, as in Galli, running from below upward into the maxillary sinuses. The extent of the turbinate and the richness in mucosa is probably greater in all mammals than in birds; certainly this seems true of Carnivora and Ungulata _versus_ Accipitres and Galli. If the seriousness of a rhinitis be dependent upon the extent of involvement of the sinuses and the blocking up of their outlets it would be expected that the variety of animal having the smallest drainage channels would show the greatest evidence of these diseases. Our records would indicate that 32 birds (.96 per cent. of the autopsies upon Aves) had rhinitis whereas only 7 mammals (.39 per cent. of autopsies on this class) presented the condition. Extension to the sinuses occurred in only one-third of each of these figures, a complication which in turn produced generalized infection more often in mammals than in birds as 4 is to 3. These figures are perhaps too small for conclusions but it would seem that rhinitis occurs more often in birds with their small sinuses and channels while sinusitis and general infection occur more often in mammals with their large sinuses and extensive turbinate apparatus. The most conspicuous orders represented are, in line of numbers Anseres 12, Psittaci 7, Accipitres 5, Carnivora 3. Nine of the twelve waterfowl were part of an epizoötic which will be discussed under specific diseases. Bacteriologically the mammalian cases that have been worked out were due to _Streptococcus pyogenes_ in several instances, including the generalized cases, and to a mixture of streptococci, golden staphylococci and members of the colon-aerogenes group. In one case in a tapir a member of the B. septicus group was found. Moulds were discovered in three avian cases and filaria in one. No pentastomum or œstrus has been discovered. In thirteen instances the lungs have been involved, apparently secondary to the nasopharyngeal disease.