OS ETHMOIDES. 79 



pyramids ; one at the base opening directly into the nose, near 

 the situation of the opening of the sphenoida). sinuses, in the 

 bones of adults ; and the other in each of the sides in contact 

 with the azygos process. './ 



This account of M. Berlin has been adopted by Sabatier, and also by Boyer, 

 who has improved it by the additional observation, that these triangular bones 

 are sometimes united to the ethmoid, and remain attached to that bone when it 

 is separated from the os sphenoides. Bichat and Fyfe have confirmed the 

 description of Boyer. 



The specimens of ethmoid and sphenoid bones, herewith exhibited to the 

 society, will demonstrate that in certain subjects, about two years of age, there 

 are continued from the posterior part of the cribriform plate of the ethmoid, two 

 Hollow Triangular Pyramids, which, when in their proper situations, receive be- 

 tween them the azygos process of the os sphenoides. (See Plate X. Figures 1, 

 2, 3, with the explanation.) 



The internal side of each of these pyramids applies to the aforesaid azygos 

 process ; the lower side of each forms part of the upper surface of the posterior 

 nares ; the external side at its basis is in contact with the orbit ar process of the 

 os palati. The base of each pyramid forms also a part of the surface of the 

 posterior nares, and contains a foramen which is ultimately the opening into the 

 sphenoidal sinus of that side. 



In the sphenoidal bones, which belong to such ethmoids as are above described, 

 there are no cells or sinuses ; for the pyramid of the ethmoid bones occupy their 

 places. The azygos process, which is to become the future septum between the 

 sinuses, is remarkably thick, but there are no cavities or sinuses in it. 



The sides of the pyramids, which are in contact with this process, are ex- 

 tremely thin, and sometimes have irregular foramina in them, as if their osseous 

 substance had been partially absorbed.* That part of the external side of the 

 pyramid which is in contact with the orbitar process of the os palati is also thin, 

 and sometimes has an irregular foramen, which communicates with the cells of 

 the aforesaid orbitar process. 



Upon comparing these perfect specimens of the ethmoid and sphenoidal bones 

 of the subject about two years of age, with the os sphenoides of a young subject 

 who was more advanced in years, it appears probable that the azygos process 

 and the sides of the pyramid applied to it, are so changed, in their progress of 

 life, that they simply constitute the septum between the sinuses ; that the exter- 

 nal side of the pyramid is also done away, and that the front side and the basis 

 of the pyramid only remain ; constituting the Cornets Sphenoidaux f of M. 

 Berlin. 



If this be really the case, the origin of the sphenoidal sinuses is very intel- 

 ligible. 



* 



* See e, Fig. 3. 



t " Cornet" is the word applied by several French anatomists to the Ossa Turblnati of 

 the nose ; they seem to have intended to express by it a convoluted lamina or plate of bone. 



The fine drawing of the Ethmoid Bone, for this plate was done by my friend M. Lesueur, 

 whose talents are so conspicuous in the plates attached to Peron's " Voyage de Descou- 

 vertes aux Terres Australes. 



