CH. VII] 



SERIAI SECTIONS 



191 



ORDER OF PROCEDURE IN MAKING MICROSCOPICAL PREPARATIONS BY THE 



PARAFFIN METHOD. 



# 300. It will be seen from this table and from sections 283 to 299 that it re- 

 quires from 5 to 7 days to get a microscopical preparation by the paraffin method 

 if one starts with a fresh tissue. Depending on the method of fixing and harden- 

 ing, the time may be much greater. Much time will be lost in waiting unless one 

 plans ahead in histological work. 



Fixing and hardening the tissue or 



organ (§ 284), 4 days or more. 

 Dehydrating the object to be cut in 



95% or stronger alcohol ($ 285), 



1 to 24 hours. 

 Displacing the alcohol and clearing 



tissues with cedar-wood oil. (See 



I 286), 2 to 24 hours. 

 Infiltrating the tissue with paraffin 



in the paraffin oven (§ 286), 2 to 



24 hours. 

 Imbedding in paraffin ($ 287), 10 



minutes. 

 Cutting the sections (| 288), 10 min- 

 utes. 

 Extending the sections with warm 



Water. (See \ 289.) 

 Fastening the sections to a slide 



{\ 290), 5 minutes to 24 hours. 

 Removing the paraffin (£291), 10 



minutes to 24 hours. 

 Removing the xylene or benzin 



(3 292). 



11. Washing with water, note, p. 180. 



12. Staining with an aqueous dye 



($ 294), 2 minutes to 24 hours. 



13. Washing away the superfluous stain 



with water {\ 294).) 



14. Staining with a general dye (§ 295- 



296), 10 seconds to 10 minutes. 



15. Washing the sections with water 



{\ 295-296). 



16. Dehydrating the stained sections in 



95% alcohol {\ 297), 3 minutes to 

 24 hours. 



17. Clearing the sections (§ 298) 2 min- 



utes to 24 hours. 



18. Mounting in Balsam {\ 299), 1 to 5 



minutes. 



19. Sealing the cover-glass (\ 253), 2 



minutes. 



20. Labeling the preparation ($ 30S), 2 



minutes. 



21. Cataloging the preparation (§ 309), 



5 to to minntes. 



SERIAL SECTIONS 



\ 301. In histological studies it is frequently of the greatest advantage to 

 have the sections in serial order, then an obscure feature in one section is fre- 

 quently made clear by the following or preceding sections. While serial sections 

 are very desirable in histological study, they are absolutely necessary for the solu- 

 tion of morphological problems presented in complex organs like the brain, in 

 embryos and in minute animals where gross dissection is impossible. 



\ 302. Arrangement of Tissues for Sections in Histology. — They should be so 

 arranged that the exact relations of each part to the organ can be readily deter- 

 mined. For example, an organ like the intestine, a muscle or a nerve, should be 

 so arranged that exact transections or longisections can be made. Organs like the 

 liver and other glands, the skin, etc., should be so arranged that sections parallel 

 with the surface or at right angles to it, (surface or vertical sections) maybe 

 made. Oblique sections are often very puzzling. 



