OCR Text |
Show 576 DR. J. SYMINGTON ON THE [Nov. 17, to one of my Australian pupils, Mr. C. Hardcastle, not only for procuring me the specimen, but also for the trouble he took to have it carefully hardened. In consequence of the elongated form of the face, the position of the nostrils towards the anterior end of the beak, and the prolongation of the hard palate backwards nearly as far as the glenoid cavity, the nasal cavities are of considerable length. In my specimen, which measured 37 cm. from the tip of the bill to the posterior extremity of the tail, the nasal cavities were 6 cm. in length. Males are considerably larger than females, and Mr. Oldfield Thomas (7) found the basal length of the skull of an adult male, measured from the basion to the anterior end of the premaxillary bones, to be 10*8 cm. The nasal cavities are not, of course, equal to the basal length of the skull, but in this male they would be quite 8 cm.; while the nasal cavities are very long their transverse and vertical diameters are very slight, so as to make their naked-eye examination somewhat difficult. The anterior parts of the nasal cavities are flattened, like the bill, from above downwards, and here the transverse diameter is about 4'5 m m . and the vertical extent scarcely 2 m m . Farther back, under the cranial cavity, and especially in the region of the turbinated processes, the nasal cavities are much deeper, measuring from the roof to the floor 5 mm., while their transverse diameter is almost obliterated by the projection of the turbinals from the outer wall. Vertical transverse sections of the nasal cavities immediately behind the nostrils show a subdivision of each cavity into 3 compartments- superior, middle, and inferior (see Plate XLIII. fig. I). The two septa between these compartments are formed by the lining membrane of the nose, which is here composed of dense connective tissue, the matrix of which is only slightly fibrillated, and of stratified squamous epithelium. The septa are not supported by any skeletal framework, but contain a few small glands the ducts of which open into the middle compartment. Serial sections show that the septa commence anteriorly as horizontal ridges projecting from the sides of the partition between the two nostrils and unite with the outer walls of the nasal cavities just behind the two nostrils. In my sections the middle compartment is always larger than the others, but this difference becomes more obvious as one passes backwards, the superior and inferior compartments gradually becoming smaller and ultimately end blindly, while the middle one becomes continuous with the main cavity of the nose. The two caecal pouches extend backwards to a little beyond the anterior end of Jacobson's organ and nearly as far as the naso-palatine foramen. Their length is about 3 mm., and the upper is a trifle longer than the lower. J. F. Meckel is the only author who, so far as I have been able to ascertain, makes any reference to this peculiar arrangement. In plate vii. fig. 8 of his classical work on the Ornithorhynchus (1), he gives a view of the anterior part of the right nasal cavity with its three divisions. He exposed them by cutting through the outer wall of the nose and turning its roof over to the left side. Meckel |