Abstract
There have been a good deal of studies published on human paranasal sinus, and its formation was discussed by Welcker, Zuckerkandl, Anton et al. But none of themm was of complete satisfaction. In the present study, canine frontal sinus was examined in the light of comparative anatomy and the results obtained were as follows :
1. On one side of the dog's frontal bone, generally, there are two cavities, A and B, but very rarely three cavities are formed by separation. The anterior cavity (A) of the two cavities is small and the posterior one (B) is large.
2. A-cavity, which is large, is irregular in shape, while B-cavity, which is small, is found very simple.
3. Both A- and B-cavities are larger in male than in female and larger on the right side than on the left side.
4. There grow many creeks in the frontal sinus, especially, in the posterior wall of Acavity.
5. Into the orifice of frontal sinus, ethmoidal concha intrudes showing turbinals, the most cases of which are seen in A-aperture sinus, where they show outside turbinals, but in the case of B-cavity, they show inside ones.
6. Both A- and B-cavities lead to the dorsal ethmoidal meatus.
7. The author is of the opinion that A-cavity is the original frontal sinus, while B-cavity is a kind of the growth from the frontal cellules.
