1 68 



PARAFFIN SECTIONING. 



\CH. VII 



ORDER OF PROCEDURE IN MAKING MICROSCOPICAL PREPARATIONS BY THE 



PARAFFIN METHOD. 



\ 284. It will be seen from this table and from sections 268 to 283 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. Unless mush time is lost in waiting one must 

 plan ahead in histological work. 



1. Fixing and hardening the tissue or 



organ ($ 269), 4 days or more. 



2. Dehydrating the object to be cut in 



95% or stronger alcohol 



270 



1 to 24 hours. 



3. Displacing the alcohol and clearing 



tissues with cedar-wood oil. (See 

 \ 271), 2 to 24 hours. 



4. Infiltrating the tissue with paraffin 



in the paraffin oven ( \ 271 ), 2 to 

 24 hours. 



5. Imbedding in paraffin (§ 272), 10 



minutes. 



6. Cutting the sections (g 273), 10 min- 



utes. 



7. Extending the sections with warm 



water. (See \ 274, 274a. ) 



8. Fastening the sections to a slide 



(3 275), 5 minutes to 24 hours. 



9. Removing the paraffin {\ 276), 10 



minutes to 24 hours. 

 10. Removing the xylene or benzin 

 (2 2 77)- 



14 



15 



n. Washing with water, note, p. 162. 



12. Staining with an aqueous dye 



($ 2 79). 2 minutes to 24 hours. 



13. Washing away the superfluous stain 



with water (| 279). 



Staining with a general dye (# 280- 



280a), 10 seconds to 10 minutes. 



Washing the sections with water 

 (J 28o-28oa). 



16. Dehydrating the stained sections in 



95% alcohol (§ 281), 3 minutes to 

 24 hours. 



17. Clearing the sections {\ 282), 2 min- 



utes to 24 hours. 



18. Mounting in Balsam (? 283), 1 to 5 



minutes. 



rg. Sealing the cover-glass ( $ 238 ) , 2 

 minutes. 



20. Labeling the preparation (g 292), 2 



minutes. 



21. Cataloging the preparation {\ 294), 



5 to 10 minutes. 



SERIAL .SECTIONS. 



§ 285. In histological studies it is frequently of the greatest advant- 

 age to have the sections in serial order, then an obscure feature in one 

 section is frequently made clear by the following or preceding sections. 

 While serial sections are very desirable in histological study, they are 

 absolutely necessary for the solution of morphological problems pre- 

 sented in complex organs like the brain, in embryos and in minute 

 animals where gross dissection is impossible. 



§286. 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 determined. For example, an organ like the in- 

 testine, a muscle or a nerve, should be so atranged that exact transec- 



