Olfactory Apparatus in Dog, Cat and Man 37 



Methods for Gross Dissection. 



The nitric acid method was used for gross dissection. The head was 

 placed in 20 per cent nitric acid for 6-12 hours, depending upon the 

 size; the decalcification had then proceeded so far that the bone could 

 be easily cut. 



The bones were removed from the nose and orbit, thus exposing the 

 olfactory bulb, the nasal mucosa and the lining of the maxillary, frontal 

 and sphenoidal sinuses. 



As the bone was removed from the mucosa the deepest or attached 

 surface of mucosa was exposed (Figs. 5, 6). It is this surface which 

 must be exposed to view them. 



In dog and cat the ethmo-turbinal bones were easily removed, as they 

 are not perforated by the nerve bundles. In man, however, this is not so 

 easily accomplished. The turbinated bones are filled with small canals 

 through which the nerve bundles pass (Fig. 11). There is, therefore, an 

 interweaving of bone and nerve. Much care is necessary to free these 

 bundles without injury. If the specimen is favorable there is a marked 

 contrast between the white nerves and the darker mucosa. This differ- 

 entiation is destroyed if the material is left too long in nitric acid. 

 The olfactory nerves are very prominent and are spread out in a fan- 

 shaped manner upon the olfactory folds. They stand out with remark- 

 able sharpness as white cords against the darker background of the nasal 

 mucosa (Figs. 5, 6). This is also true of the branches of the 5th nerve 

 which innervate the nose. It is this differentiation and the fact that 

 the nerves lie in the deeper layers of the mucosa next to the bone which 

 made this dissection of the fine terminal branches of the 5th nerve 

 possible. Even under these favorable circumstances it was necessary 

 to dissect under water and in brilliant light (sunlight or electric light) 

 with a magnifier giving 8-13 diameters. 



Material prepared by the nitric acid method may be preserved during 

 the dissection in 3 per cent formalin without markedly changing color. 

 This does not hinder the dissection and material will not deteriorate in 

 it. Five per cent formalin is recommended for permanent preservation. 



If material preserved in formalin is used, further decalcification may 

 not be necessaiy. There will, however, be no differentiation in color 

 between the mucosa and the nerves, and the material, therefore, does 

 not give as satisfactory results. 



