THE OLFACTORY ORGAN. 281 



kinds of preparations. The large fat droplets in 

 some of the epithelium cells of the uppermost turn 

 are peculiar to the guinea-pig, as is also the arched 

 projection seen in the sections at the part where 

 these cells are found. The fat drops are stained 

 black in the osmic preparation. 



THE OLFACTORY ORGAN. 



Preparations 1-3. Small pieces of the upper 

 turbinate bones, or from the upper (olfactory) region 

 of the septum nasi,from the dog or rabbit, are placed, 

 one piece in one-sixth per cent of chromic acid solu- 

 tion, a second in one-fourth per cent, of bichromate 

 of potash, and a third in one per cent, of osmic acid. 

 The one in chromic acid may remain a week, when 

 it is transferred to weak spirit and in twenty-four 

 hours more to strong spirit. After a day or two in 

 this, vertical sections are prepared from it. 



The other two pieces are examined after forty-eight 

 hours' maceration, small pieces of the mucous mem- 

 brane being teased out so as to isolate the epithelium 

 cells (both columnar and spindle-shaped), and if pos- 

 sible, especially in the osmic preparations, to study 

 the connection of their branching lower ends with 

 subjacent structures. These preparations can be pre- 

 served with glycerine, the bichromate one being 

 stained with logwood. 



Preparations 4 and 5. Teased preparations 

 should also be made of the olfactory mucous mem- 

 brane of the frog or newt. Having cut oft' the head 

 of the animal, and slit up the nostrils with fine scis- 

 sors, place it in a quantity of one-fourth per cent, 

 solution of bichromate of potash. After two days' 

 preparations of the epithelium from both the anterior 

 and posterior part of the passage may be made. The 

 cells are obtained with the greatest ease, by scraping 

 the mucous surface with the point of a scalpel, and 

 shaking out the material in a drop of water on a 

 slide. A piece of hair is added, and the preparation 



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