The paranasal sinuses can be seen in animals higher than reptiles, and 13 different types of paranasal sinuses are known to exist in various animals. There is, however, no generally accepted concept regarding its entity and function.
The author proposes the following view concerning the advent of the paranasal sinuses in animals and man.
The maxillary sinus and the frontal sinus appear around the ethmoturbinate which is essentially an olfactory organ.
In order to adapt to the erect position and to obtain a secure foundation for strong muscles of mastication, the facial bone has been gradually transformed, during which process secondary sinuses have come in to existence. The paranasal sinuses had been beneficial for lightening the weight of the head and for obtaining a buffer effect on impacts. Due to the advancements of visual organs in primates, the ethmoid bone had regressed to a smaller cavity.
In man, further enlargement of the maxillary sinus occurred due to retraction of the facial cranium and enlargement of the molar teeth.
In the process of hominization even further enlargement of the frontal and the sphenoid sinuses took place.
The paranasal sinuses therefore seem to have developed during the process of advance of animals per se and particularly the advance of the olfactory organ, respiratory organ and the brain by means of both the allometry and the preadaptation phenomena.
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